Compound semiconductor particles and production process therefor

ABSTRACT

There are provided: compound semiconductor particles that can display more excellent performance in functions peculiar to the compound semiconductor (e.g. luminosity and luminescence efficiency); and a production process for obtaining such compound semiconductor particles with economy, good productivity, and ease. Compound semiconductor particles, according to the present invention, are characterized by comprising body particles and a metal oxide, wherein the body particles have particle diameters of smaller than 1 μm and are covered with the metal oxide and include a compound semiconductor including an essential element combination of at least one element X selected from the group consisting of C, Si, Ge, Sn, Pb, N, P, As, Sb, S, Se, and Te and at least one metal element M that is not identical with the element X, and wherein the metal oxide is a metal oxide to which an acyloxyl group is bonded.

TECHNICAL FIELD

The present invention relates to compound semiconductor particles and aproduction process therefor.

BACKGROUND ART

It has hitherto been known that: particles including a so-calledcompound semiconductor such as ZnS and CdSe (also including compoundsemiconductors doped with such as Ag and Mn) (compound semiconductorparticles) have various useful functions such as of being able to emitfluorescence by irradiating the particles with ultraviolet rays and/orelectron beams as excitation sources or applying a voltage to theparticles (e.g. U.S. Pat. No. 5,455,489). In addition, in recent years,as to compound semiconductor particles including such as CdSe andMn-doped ZnS, it is being verified on a research level and thus becomingclear that, if the particles are more fined to thereby be quantum-sized,then the particles become excellent in various functions, for example,there can be obtained particles having a high luminance of thefluorescence.

However, the compound semiconductor particles generally have a problemsuch that, if the compound semiconductor particles are quantum-sized,then they become unable to sufficiently perform their peculiarfunctions, for the reason such that: the particles are lacking in heatresistance, and their surfaces become more easily oxidized. Thus, it isthought that: the particles are lacking in stability and durability andare very difficult to put to practical use. In addition, in the casewhere the particles are fined to thereby be quantum-sized, it becomesmore and more difficult to maintain a favorable monodispersed state.However, unless the compound semiconductor particles are in such afavorable monodispersed state, for example, there is a problem that:their luminosity greatly decreases, and further there is a problem thatthe properties such as luminescence greatly vary also with the kinds ofdispersants as used for dispersing the particles.

On the other hand, as is mentioned above, the dispersed state of thecompound semiconductor particles has a great influence on such as theirluminosity and/or luminescence efficiency. Thus, in order to treat thecompound semiconductor particles in a state where their primaryparticles are isolated from each other (in the monodispersed state),there have hitherto been made the following proposals.

First, there has been proposed a method that involves treating thesurfaces of CdSe particles with ZnS (for example, M. G. Bawendi et al.,“J. Phys. Chem. B”, volume 101, pages 9463 to 9475 (published in 1997)).However, as to this method, the compound semiconductor particles whichare inherently lacking in chemical durability (e.g. oxidationresistance) and thermal durability are merely treated with the similarcompound semiconductor. Therefore, even if the properties aretemporarily enhanced, there is a problem of lacking the practicabilityafter all.

In addition, there has been proposed a method that involves attachingoxide particles (e.g. zinc oxide, indium oxide and silica) to surfacesof micron-sized sulfide-type fluophor particles (for example,JP-A-104684/1989 and JP-A-041389/1990). However, as to this method, theattachment of the oxide particles to the compound semiconductorparticles needs a heat-treatment step at a high temperature after theattachment-treatment step. Therefore, there are problems such that: themovement of substances and the defectiveness occur during this heatingat the high temperature to greatly deteriorate the luminescenceproperty; and there are economical disadvantages of increasing such astreatment costs, and it is necessary to involve a complicated treatmentstep, so the productivity is inferior.

Furthermore, in recent years, there have been proposed some methods thatinvolve covering a nano-sized level of fluophor particles with such assulfides, oxides, and other inorganic substances (for example, U.S. Pat.No. 5,985,173, JP-A-265166/2000, Japanese Patent No. 2514423, andJapanese Patent No. 2946763). However, these methods, for example, havethe following prior problems: the chemical and thermal stabilities areinsufficient; the monodispersibility is so inferior that the excellentfluorescence property as expected by the nano-sizing cannot sufficientlybe displayed; and also, the economy is poor, and the productivity isinferior.

DISCLOSURE OF THE INVENTION OBJECT OF THE INVENTION

Accordingly, an object of the present invention is to provide: compoundsemiconductor particles that can display more excellent performance infunctions peculiar to the compound semiconductor (e.g. luminosity andluminescence efficiency); and a production process for obtaining suchcompound semiconductor particles with economy, good productivity, andease.

SUMMARY OF THE INVENTION

The present inventors diligently studied to solve the above-mentionedproblems.

As a result, they have found that: if nano-sized superfine compoundsemiconductor particles are compound semiconductor particles coveredwith a metal oxide to which an acyloxyl group is bonded, then they areparticles having excellent chemical and thermal durability and also goodmonodispersibility, and therefore the properties as enhanced by theabove nano-sizing can be displayed sufficiently, and besides, there issurprisingly also a case where the above enhanced properties can befurther extensively displayed.

Furthermore, the present inventors have found out that: if, when theparticles including a compound semiconductor are covered, there isheated or polish-pulverized a mixture obtained by further adding theparticles including the compound semiconductor to a mixture including ametal carboxylate and an alcohol or to a mixture including ametal-alkoxy-group-containing compound and a carboxyl-group-containingcompound, then a reaction to form the metal oxide from the metalcarboxylate and the alcohol or from the metal-alkoxy-group-containingcompound and the carboxyl-group-containing compound in the presence ofthe particles including the compound semiconductor is caused by heat dueto the aforementioned heating or by heat as generated by the frictionalforce during the aforementioned polish-pulverization, so that thecompound semiconductor particles as covered (specifically, with themetal oxide) are obtained economically and easily.

In addition, the present inventors have found that: if the abovecompound semiconductor particles as covered with the metal oxide areobtained by a production process including specific steps, thensurprisingly the peculiar functions and properties (e.g. luminescenceproperty) are further greatly enhanced.

The present inventors have completed the present invention by confirmingthat the compound semiconductor particles and production processtherefor, as based on the above findings, could solve the above problemsat a stroke.

That is to say, compound semiconductor particles, according to thepresent invention, are characterized by comprising body particles and ametal oxide, wherein the body particles have particle diameters ofsmaller than 1 μm and are covered with the metal oxide and include acompound semiconductor including an essential element combination of atleast one element X selected from the group consisting of C, Si, Ge, Sn,Pb, N, P, As, Sb, S, Se, and Te and at least one metal element M that isnot identical with the element X, and wherein the metal oxide is a metaloxide to which an acyloxyl group is bonded.

A first production process for compound semiconductor particles,according to the present invention, is characterized by comprising thestep of heating and/or polish-pulverizing a mixture including a metalcarboxylate, an alcohol, and particles or a mixture including ametal-alkoxy-group-containing compound, a carboxyl-group-containingcompound, and particles, thereby covering the particles with a metaloxide, wherein the particles include a compound semiconductor.

A second production process for compound semiconductor particles,according to the present invention, is characterized by comprising thesteps of: polish-pulverizing coarse particles of a compoundsemiconductor to thereby obtain particles having particle diameters ofsmaller than 1 μm; and then covering the resultant particles with ametal oxide.

EFFECTS OF THE INVENTION

The present invention can provide compound semiconductor particles thatcan display more excellent performance in functions peculiar to thecompound semiconductor (e.g. luminosity and luminescence efficiency).Also, the present invention can provide a production process forobtaining such compound semiconductor particles with economy, goodproductivity, and extreme ease.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an electron micrograph showing a TEM image of the fine CdSeparticles having particle diameters of about 19 nm as obtained inExample 1.

FIG. 2 is an electron micrograph showing a TEM image of the fine CdSeparticles having particle diameters of about 19 nm or not larger than 10nm as obtained in Example 2.

FIG. 3 is an electron micrograph showing a TEM image of the fine CdSeparticles as obtained in Example 7.

FIG. 4 shows results of the elemental analysis of the fine CdSeparticles, as obtained in Example 7, by the energy-dispersive X-rayanalysis method. Fig. (a) shows a mapping as to the Zn element, and Fig.(b) shows a mapping as to the Zn element and the Cd element.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, detailed descriptions are given about the compoundsemiconductor particles and the production process therefor according tothe present invention. However, the scope of the present invention isnot bound to these descriptions. And other than the followingillustrations can also be carried out appropriately within the scope notdeparting from the spirit of the present invention.

[Compound Semiconductor Particles]:

The compound semiconductor particles according to the present inventionare particles of which the body particles including the compoundsemiconductor are covered. By being covered with the metal oxide, thebody particles including the compound semiconductor become particles ofwhich such as the chemical durability (e.g. oxidation resistance) andthermal durability have easily been enhanced, and besides, of which themonodispersibility is excellent. As a result, the particles become ableto sufficiently and stably display their functions and propertiespeculiar to compound semiconductor particles. Furthermore, if variousconditions such as the kind of the covering substance and the coveringamount (e.g. area and thickness) are controlled, then it is alsopossible to control the enhancement of the functions and properties ofthe compound semiconductor particles and to control theirmonodispersibility.

Although there is no especial limitation on the peculiar functions andproperties possessed by the compound semiconductor particles, yetexamples thereof include: semiconductor functions, such as luminescenceproperty (fluorescence emission), electronic conductivity, andphotoconductivity; (photo)magnetic functions, such as ferromagnetism andmagnetic optical properties; and magnetic semiconductor functions. Ofthe above, the luminescence property can effectively be enhanced by theabove covering.

The compound semiconductor, constituting the compound semiconductorparticles according to the present invention or the above bodyparticles, refers to a compound semiconductor including an essentialelement (element constituting the compound) combination of at least oneelement X selected from the group consisting of C, Si, Ge, Sn, Pb, N, P,As, Sb, S, Se, and Te and at least one metal element M that is notidentical with the element X (such a compound semiconductor mayhereinafter be referred to as compound semiconductor A). As the metalelement M, there can be used at least one member selected from among:group 1A, group 2A, group 3A, group 4A, group 5A, group 6A, group 7A,group 8, group 1B, group 2B, group 3B, group 4B (excluding C), group 5B(excluding N), group 6B (excluding O and S), lanthanoide elements, andactinoide elements in the periodic table. Incidentally, herein,“Periodic table of elements (published in 1993)” shown in the 5thedition of “Chemical Handbook (edited by the Chemical Society of Japan)”(published by Maruzen Co., Ltd.) is used as the periodic table, and thegroup numbers are shown by a system of subgroup notation.

The compound semiconductor, constituting the compound semiconductorparticles according to the present invention or the above bodyparticles, will do if it is a compound including the above element X andmetal element M. Examples thereof include: compounds of which a part ofmetal elements M are displaced with H (hydrogen atoms) (also includingcompounds in which the H are used as the second, third, fourth, . . .metal elements M in the case of the below-mentioned mixed crystal); andbesides, compounds of which a part of elements X are displaced with O(oxygen atoms). Thus, there is no especial limitation. In addition,there is no especial limitation on the doping element for thebelow-mentioned solid solution. Any element can be selected and thenused.

Incidentally, in the present invention, the aforementioned compoundsemiconductor A is not necessarily limited only to the compound havingthe above-mentioned functions and properties peculiar to semiconductors.The compound semiconductor A may include a compound having very lowsemiconductor properties and/or a compound having no semiconductorproperties if it includes the combination of the above elements X and M.

As to the compound semiconductor A, for example, so-called III-Vcompounds, II-VI compounds, IV-IV compounds, IV-VI compounds, and M-Xcompounds containing group 2A elements as M are favorable as M-Xcompounds. Direct transition type III-V compounds and II-VI compoundsare favorable as compound semiconductors having the luminescenceproperty.

The III-V compounds are compounds including a combination of a group 3Belement as the M and a group 5B element as the X in the periodic table.Specific examples thereof include GaAs, GaAsP, GaAlAs, AlP, InP, GaP,InGaAlP, AlS, GaN, InGaN, BN, InSb, GaSb, and nitrides of BAlGaIn. Ofthe above, such as GaN, InGaN, GaAs, and GaAsP are cited as compoundshaving an excellent luminescence property.

The II-VI compounds are compounds including a combination of a group 2Belement as the M and a group 6B element (excluding the oxygen) as the Xin the periodic table. Specific examples thereof include ZnS, ZnSe,ZnTe, CdS, CdSe, CdTe, HgS, HgSe, and HgTe. Of the above, such as CdS,CdSe, ZnSe, ZnS, and ZnMgSe are cited as compounds having an excellentluminescence property.

The IV-IV compounds are compounds including a combination of group 4Belements as the M and X in the periodic table. Specific examples thereofinclude SiC and SiGe. Of the above, such as SiC is cited as a compoundhaving an excellent luminescence property.

The IV-VI compounds are compounds including a combination of a group 4Belement as the M and a group 6B element (excluding the oxygen) as the Xin the periodic table. Specific examples thereof include SnTe, PbS,PbSe, and PbTe. Of the above, such as PbTe is cited as a compound havingan excellent luminescence property.

Examples of the M-X compounds, containing group 2A elements as M,include MgS, CaS, SrS, BaS, CaSrS, SrSe, BaSe, and CaTe.

In the present invention, the compound semiconductor A may be in theform of a mixed crystal. Examples of the mixed crystal of the compoundsemiconductor generally include three-element-mixed crystals,four-element-mixed crystals, five-element-mixed crystals, andsix-element-mixed crystals. As to the above two-element compounds suchas the III-V compounds, their various chemical and physical propertiesare unambiguously determinate, so there is no room to artificiallycontrol them. However, if the compound semiconductor is in the form ofthe mixed crystal, the properties can be controlled by the mixing ratiobetween the elements. For example, it is also possible to set thelattice constant and the band structure independently of each other.

In the present invention, the compound semiconductor A is referred to asthe M-X compound as mentioned above. This M-X compound is not limited toa compound having a definite-ratio composition (for example, in the caseof CdSe, Cd:Se=1:1). The M-X compound may be a compound having anindefinite-ratio composition (e.g. Cd_(0.98)Se_(1.0) compound) or amixture of the compound having the definite-ratio composition and thecompound having the indefinite-ratio composition. Thus, there is noespecial limitation. In addition, herein, in the case where the M-Xcompound is a compound having a mixed crystal form, then, for example,the forms as generally shown by Cd_(1-x)Zn_(x)Se_(1-y)S_(y) andCd_(1-x)Zn_(x)Se₁ are referred to simply as CdZnSeS and CdZnSerespectively. Accordingly, for example, InGaN refers to not the form ofIn:Ga:N=1:1:1 in elemental ratio, but In_(0.1)Ga_(0.9)N_(1.0), which isa compound form having a definite-ratio composition, and/or a compoundform of it having an indefinite-ratio composition.

In the present invention, the compound semiconductor A may be in theform of a solid solution as doped with a different kind of metal elementor non-metal element (e.g. ZnS doped with Mn). Preferred examples of thedifferent kind of metal element or non-metal element as used for thedoping include: typical metal ions as luminescent-center metals, such asSb³⁺, Sn²⁺, Pb²⁺, and Tl⁺; transition metal ions such as Mn²⁺, Cr³⁺,Ag⁺, and Cu²⁺; rare earth metal ions such as Ce³⁺, Ce⁴⁺, Eu²⁺, Eu³⁺,Tb³⁺, Er³⁺, Sm³⁺, Nd³⁺, Ho³⁺, and Yb³⁺; and halogen atoms such as F andCl. They can give effects such as of displaying such a sharpluminescence property as to be narrow in luminescence wavelength width.

As to the body particles including the compound semiconductor andconstituting the compound semiconductor particles according to thepresent invention, their particle diameters are favorably in thenano-sized range of smaller than 1 μm, more favorably smaller than 0.1μm, still more favorably smaller than 0.01 μm. If the particle diametersare in the nano-sized range, then the peculiar functions and propertiesinherently possessed by the compound semiconductor particles aredisplayed with higher efficiency due to the quantum effects. Forexample, also as to particles having the luminescence property, it canbe considered that: (1) higher luminescence efficiency can be displayed;(2) the narrowing of the luminescence wavelength width can display theluminescence property of a higher luminance, and further (3) theluminescence wavelength can be controlled by regulating the particlediameters because the luminescence is made by the quantum effects. Suchenhancement of the functions and properties is more sufficientlydisplayed by the covering (as referred to in the present invention) ofthe particles. The effects as obtained by the covering (as referred toin the present invention) of the particles are particularly remarkablein the case where the objects of the covering are the above compoundsemiconductor particles having the nano-sized range of particlediameters.

The compound semiconductor particles according to the present inventionare particles covered with the metal oxide. There is no especiallimitation on the metal oxide provided to the covering. Preferredexamples thereof include metal oxides having properties as n-typesemiconductors, p-type semiconductors, insulators, and dielectrics, andit is possible to adopt oxides of the elements that are previously citedas examples of the aforementioned metal element M. The metal oxideprovided to the covering may be a single metal oxide, or a compositeoxide, or a solid solution oxide. In the case where compoundsemiconductor particles having the luminescence property are used as thebody particles and as luminophors, usually, it is favorable to cover thebody particles with a metal oxide having a band gap on theshorter-wavelength side of the light-absorption wavelength and/orluminescence wavelength of the body particles. Examples of such a metaloxide include ZnO, SnO₂, and In₂O₃, and SiO₂.

In addition, the crystallinity of the metal oxide provided to thecovering may be either crystalline or noncrystalline in electrondiffraction and/or X-ray diffraction.

The form of the metal oxide provided to the covering may be either aparticulate form or another form. Thus, there is no especial limitation.

Preferred examples of the metal oxide provided to the covering includethe same as the metal oxide as formed in the below-mentioned firstproduction process according to the present invention.

In the present invention, there is no especial limitation on thecombination of the compound semiconductor (constituting the bodyparticles) and the metal oxide (provided to the covering) (thiscombination is hereinafter referred to as “compound semiconductor/metaloxide”). However, specifically preferred examples thereof include“CdSe/ZnO”, “CdS/ZnO”, “ZnSe/ZnO”, “ZnS/ZnO”, “CdSSe/ZnO”, “InGaN/ZnO”,“ZnCdS/ZnO”, “PbTe/ZnO”, “CdSe/In₂O₃”, “CdSe/SiO₂”, and “CdSe/SnO₂”.Incidentally, the metal oxides provided to the covering are simply shownby such as ZnO, In₂O₃, SnO₂, and SiO₂ in the above way. However, thesemay, for example, have either an oxygen-defective composition (e.g.ZnO_(0.98)) (oxides possible to form n-type semiconductors are usuallyapt to be in a metal-excess state) or a metal-deficient composition(oxides possible to form p-type semiconductors are usually apt to be ina metal-deficient state), or their mixture.

The covering with the metal oxide further has the following advantages.That is to say, the metal oxide surface easily adsorbs or reacts withsuch as various organic functional groups, metal hydride groups, andmetal alkoxy groups. In addition, it is easy to introduce such asvarious organic compounds, coupling agents (e.g. silane couplingagents), and the below-mentioned surface-treating substance (A) into themetal oxide surface. Accordingly, as to the compound semiconductorparticles according to the present invention as covered with the metaloxide, there can easily be carried out such as the control of thedispersibility into various mediums by secondary surface-treatment withhitherto publicly known dispersants that are conventionally andgenerally used favorably for metal oxide particles. Examples of theabove organic functional group include a carboxyl group, an alkoxygroup, a phenoxy group, an amino group, a quaternary ammonium group, anamide group, an imide group, a urethane group, a ureido group, anisocyanate group, an epoxy group, and a sulfonic acid group.

In addition, as to the compound semiconductor particles according to thepresent invention, the metal compound provided to the covering is ametal oxide to which the acyloxyl group is bonded. Examples of theacyloxyl group include an acetoxy group (ethanoyloxy group), apropionyloxy group, and an 2-ethylhexanoyloxy group. However, above all,the acetoxy group (ethanoyloxy group) is particularly favorable. If themetal oxide to which the acyloxyl group is bonded is provided to thecovering, then there can further be enhanced various effects due to thecovering with the metal oxide, particularly, the dispersibility intovarious mediums. The bonding amount of the acyloxyl group in the metaloxide is favorably in the range of 0.01 to 40 mol %, particularlyfavorably 0.1 to 20 mol %, relative to the metal in the metal oxide.

The form of covering the particles in the compound semiconductorparticles according to the present invention may be a form of completelycovering the body particle (covering the entirety of the body particle)or a form of partially covering the body particle (covering a portion ofthe body particle). Although not especially limited, the form ofcovering the entirety of the body particle is favorable in considerationof the quantum effects (e.g. enhancement of the luminescence property)in the case where the body particle is a particle being in thenano-sized range.

In addition, there is no especial limitation on the thickness of thecovering. The covering may be either in the form of a single-molecularlayer of the metal oxide provided to the covering or in the form of amultiple layer of a crystal lattice of this metal oxide. In addition,the covering layer may be either noncrystalline or crystalline. The formhaving thickness to a certain extent (e.g. the multiple layer of thecrystal lattice) is preferable to the form of the single-molecular layerin consideration of the quantum effects (e.g. enhancement of theluminescence property).

In the present invention, it is favorable that the covering is madeuniformly throughout the surface of the body particle including thecompound semiconductor. Specifically, it is favorable that the coveringis made throughout the entire surface of the body particle. Or, in thecase where the covering is not made throughout the entire surface of thebody particle, it is favorable that the covered portions exist in theevenly dispersed form. Besides, it is favorable that the thickness ofthe covering is almost the same at any covered portion.

The compound semiconductor particle according to the present inventionmay include at least two body particles, but, particularly favorably,includes one body particle.

Examples of uses of the compound semiconductor particles according tothe present invention include luminophors having a high-efficientluminescence property. Specifically, the above particles can be used asfluophor particles of various colors (e.g. red (R), green (G), blue (B),and yellow (Y)) and as luminophor particles being in the ultraviolet orinfrared wavelength range.

Examples of the fluophor particles of various colors include fluophorparticles that can display a high luminance due to excitation made invarious manners (e.g. excitation by irradiation of electron beams and/orultraviolet rays, electric field excitation). Specific examples thereofinclude fluophor particles of various colors (e.g. red (R), green (G),blue (B), and yellow (Y)), wherein the fluophor particles can be usedfor a white LED possible to use as display devices (e.g. fluorescentlamps, color televisions, fluorescent display tubes, dispersed-type ELelements, thin-film-type EL elements, plasma displays, and FED (fieldemission displays)) and illumination light sources. In addition, as tomedical uses, the above fluophor particles can be used also for tumormarkers, curing medicines, and examining agents for the purpose ofdetection of tumors (e.g. cancers) or examination of such as theirprogress conditions.

In addition, examples of other uses of the compound semiconductorparticles according to the present invention include various sensors(e.g. biosensors; sensors for search of land mines, TNT(trinitrotoluene), and earth vein; and ultraviolet sensors) andwavelength-converting films.

In the case where the compound semiconductor particles according to thepresent invention are, for example, used as the fluophor particles ofvarious colors for the display devices, the particles need to uniformlybe mixed and dispersed into such as coating liquids, and it is thereforefavorable to use the particles together with a dispersant. The compoundsemiconductor particles are surface-treated (secondarily treated) withthe dispersant so that the favorable dispersibility can be displayed.Examples of usable dispersants include: various coupling agents (e.g.silane coupling agents, titanate type coupling agents, and aluminatetype coupling agents); polymer dispersants; cationic, anionic,amphoteric, and nonionic surfactants; and besides, fatty acids, organicamines, and alcohols.

In addition, as is mentioned above, the compound semiconductor particlesaccording to the present invention can be used also as the medicalmarkers. However, in that case, the particles are used after having beensurface-treated (secondarily treated) with a substance (surface-treatingsubstance (A)) as predetermined for each target (such as substance,tissue, and cell). Specific examples of the combination of thesurface-treating substance (A) and the target (“surface-treatingsubstance (A)/target”) include “biotin/actinfilament”, “urea or acompound containing a ureido group and carboxylic group/cell nucleus”,“carboxylic acid/protein, peptide, and cell nucleus”, “transferring/Helacell”, “thiol-modified DNA/DNA oligomer”, “amino-group-modified DNA/DNAoligomer”, “negative-charged lipoic acid/E. coli. Maltose bindingprotein-basic, zipper fusion protein, and prostaglandin”,“negative-charged leucine zipper/positive-charged leucine zipperattached to C terminal of recombinant protein, and avidin”.

The body particles in the compound semiconductor particles according tothe present invention, favorably, have particle diameters of smallerthan 1 μm and are obtained by a process including the step ofpolish-pulverizing coarse particles of a compound semiconductor.

The body particles in the compound semiconductor particles according tothe present invention can be obtained by the production processcomprising the step of polish-pulverizing coarse particles of a compoundsemiconductor as raw materials to thereby produce particles havingparticle diameters of smaller than 1 μm.

The polish-pulverization in the present invention, conceptually,includes pulverization, crushing, and disintegration. Specifically, thepolish-pulverization in the present invention, mainly, refers to finingwith media mills such as ball mills, beads mills, and sand mills, butalso encompasses fining with pulverization apparatuses anddisintegration apparatuses such as hammer mills. In addition, thepolish-pulverization is classified into a manner under dry conditions(dry manner) and a manner under wet conditions (wet manner), and eitherof them may be used. However, the wet manner is favorably adopted inthat the compound semiconductor particles as dispersed in a solvent candirectly be obtained, and in that the temperature control is easy tocarry out. In addition, the polish-pulverization in the presentinvention, conceptually, further includes the following finings: finingthe crystal grains by destroying the crystal at random; fining thecrystal grains by breaking the crystal walls selectively from crystalwall faces easy to break; fining the polycrystal into a crystal grainlevel by unbinding the bonding at the grain boundary between crystalgrains of the polycrystal; and fining the secondary aggregate intoprimary particles.

The above compound semiconductor, which is used as a raw material forthe body particles, may be any of a single crystal, a polycrystal, and anoncrystal. In addition, the size of the crystal grain or primaryparticle is not limited. Examples of the kind and properties (e.g.composition, crystal structure) of the above compound semiconductor,which is used as a raw material for the body particles, include the sameas those of the compound semiconductor as mentioned in the explanationof the compound semiconductor particles according to the presentinvention.

If the coarse particles of the compound semiconductor are fined by thepolish-pulverization so as to form particles having particle diametersof smaller than 1 μm (nano order), then the functions and propertiespeculiar to the compound semiconductor particles due to the quantumeffects is more enhanced than usual. For example, the luminosity, theluminance, and the luminescence efficiency are enhanced by leaps andbounds in the case of the compound semiconductor particles having theluminescence property. Although a conjecture, the reason for sucheffects can be considered to be as follows: electrons are efficientlyused for excitation of light due to the quantum effects and thenano-sizing effects, so that the obtained light can be efficiently takenout.

In the present invention, because the mixed crystal and/or solidsolution of the compound semiconductor having a uniform composition canbe used as a raw material being polish-pulverized, excellent results areprovided with regard to the uniformity of the composition and functionsof individual particles resultant from the polish-pulverization or thesubsequent surface covering.

The particle diameters of the above coarse particles of the compoundsemiconductor, which are used as raw materials for obtaining the bodyparticles of the compound semiconductor particles according to thepresent invention, are not smaller than micron order. The particlediameters will do if they are large to such an extent as can bedecreased to smaller than 1 μm (nano order) by the polish-pulverization.Thus, there is no especial limitation on the particle diameters.

There is no especial limitation on the shape of the above coarseparticles of the compound semiconductor. However, examples thereofinclude any shape such as a spherical shape, a sheet shape, a needleshape, a cubic shape, and an irregular shape.

It is favorable that the polish-pulverization for obtaining the bodyparticles of the compound semiconductor particles according to thepresent invention is carried out in a solvent. The solvent which can beused may be water. However, organic solvents are favorable, becausethere is a possibility that defects may be caused by elution of themetal element M and/or the element X from the compound semiconductorinto water. Preferred examples of the solvent include: hydrocarbons;halogenated hydrocarbons; alcohols (also including such as phenols,polyhydric alcohols, and their derivatives which arehydroxyl-group-containing compounds); ethers and acetals; ketones andaldehydes; esters; derivative compounds as formed by displacement ofactive hydrogen atoms of all hydroxyl groups of the polyhydric alcoholswith an alkyl group and/or an acetoxy group; carboxylic acids and theiranhydrides; silicone oils; and mineral oils. These may be used eitheralone respectively or in combinations with each other.

When and/or after the coarse particles of the compound semiconductor arepolish-pulverized, it is favorable that at least one member (which mayhereinafter be referred to simply as “primary-particle formationpromoter”) selected from the group consisting of carboxylic acids,halide ions, and compounds which form the halide ions in the system ofthe polish-pulverization treatment (for example, in the above solvent asused for the polish-pulverization treatment) is caused to coexist withthe coarse particles of the compound semiconductor and/or withpolish-pulverized fine particles of the compound semiconductor.Particularly above all, the carboxylic acids are favorable also from theviewpoint of not having a bad influence upon the covering reaction whenthere is carried out the reaction of covering the compound semiconductorparticles according to the present invention with the metal oxide. Andacetic acid is more favorable in that its dispersing effect is high.

Usually, as to the compound semiconductor particles as fined by thepolish-pulverization, the smaller their particle diameters are, the moreeasily the secondary aggregation occurs again. However, if the finedparticles are obtained in the coexistence with the aboveprimary-particle formation promoter, then there is easily obtained ahigh-concentration dispersion in which the above fined particles aredispersed in a primary-particle state. In addition, if the aboveprimary-particle formation promoter is added to a liquid resultant fromthe polish-pulverization, then there can easily be obtained a dispersionin which the fined particles are dispersed in the primary-particle stateby disintegrating the aggregation of the secondary aggregate includingthe fined particles.

There is no especial limitation on the method for achieving the abovecoexistence of the primary-particle formation promoter. In addition, themethod will do if the promoter is caused to exist in the systemincluding the finally polish-pulverized fine particles of the compoundsemiconductor. Therefore, there is no especial limitation on the timingof using (adding) the primary-particle formation promoter, either. Thepromoter may, as aforementioned, be used either during or after thepolish-pulverization, or may be used both during and after thepolish-pulverization. As to the timing of using the primary-particleformation promoter during the polish-pulverization, for example, thepolish-pulverization may be carried out after the following steps ofmixing the coarse particles of the compound semiconductor with thesolvent and then adding the primary-particle formation promoter to theresultant mixture. Or the polish-pulverization may be carried out afterthe following steps of beforehand adding the primary-particle formationpromoter to the coarse particles of the compound semiconductor and thenmixing the resultant mixture with the solvent. Or thepolish-pulverization may be carried out after the following steps ofbeforehand adding the primary-particle formation promoter to the solventand then mixing the resultant mixture with the coarse particles of thecompound semiconductor. Thus, there is no especial limitation on theabove timing.

There is no especial limitation on the aforementioned carboxylic acids.However, preferred examples thereof include: saturated aliphaticmonocarboxylic acids (e.g. formic acid, acetic acid, propionic acid,butyric acid, lauric acid, and stearic acid); saturated aliphaticdicarboxylic acids (e.g. oxalic acid, malonic acid, succinic acid,glutaric acid, adipic acid, and sebacic acid); unsaturated aliphatic(mono-, di-, and poly)carboxylic acids (e.g. acrylic acid, propiolicacid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, andmesaconic acid); carbon-cyclic (mono-, di-, and poly)carboxylic acids(e.g. benzoic acid, phthalic acid, terephthalic acid, naphthoic acid,toluic acid, hydratropic acid, and cinnamic acid); heterocycliccarboxylic acids (e.g. furoic acid, thenoic acid, nicotinic acid,isonicotinic acid, hydroxycarboxylic acids, and alkoxycarboxylic acids);and other carboxylic acids (e.g. glucolic acid, lactic acid, glycericacid, malic acid, tartaric acid, benzilic acid, salicylic acid,3,4-dihydroxybenzoic acid, anisic acid, and piperonylic acid). Of theabove, saturated aliphatic monocarboxylic acids having 1 to 4 carbonatoms are more favorable in that they have the high ability to disperseimpurities into solvent drops. These may be used either alonerespectively or in combinations with each other.

There is no especial limitation on the aforementioned halide ions.However, preferred examples thereof include a fluoride ion (F⁻), achloride ion (Cl⁻), a bromide ion (Br⁻), and an iodide ion (I⁻). Thesemay be used either alone respectively or in combinations with eachother.

There is no especial limitation on the compounds that form the halideions in the aforementioned system of the polish-pulverization treatment.However, preferred examples thereof include: hydrogen fluoride, hydrogenchloride, hydrogen bromide, and hydrogen iodide; and their aqueoussolutions; and their salts with alkaline metals or alkaline earthmetals. These may be used either alone respectively or in combinationswith each other.

Although not especially limited, the ratio (mixing ratio) of theaforementioned primary-particle formation promoter as added to thecoarse or fine particles of the compound semiconductor to thereby becaused to coexist therewith is, for example, favorably in the range of0.0001 to 1,000 mol % relative to the number of metal atoms contained inthe coarse particles of the compound semiconductor as used. In the casewhere the above mixing ratio is less than 0.0001 mol %, there is apossibility that the dispersing effect due to the dispersing action maynot sufficiently be displayed. In the case where the mixing ratio ismore than 1,000 mol %, the enhancement of the dispersing effect is notseen very much even if the amount as used is more increased, orotherwise there is also a possibility that the dispersing effect may belowered.

In addition, in the case where the primary-particle formation promoteris caused to coexist with the coarse or polish-pulverized fine particlesof the compound semiconductor when the aforementioned coarse particlesof the compound semiconductor is polish-pulverized, then a trace of fine(usually, particle diameters of not larger than 100 nm) impurityparticles that are usually difficult to remove can efficiently bedispersed and floated in the initial stage of the polish-pulverizationof the coarse particles. Therefore, there is further obtained an effectsuch that the resultant fine particles of the compound semiconductor canconsequently easily be purified by separating and removing a supernatantor dispersion in the initial stage of the polish-pulverization. Forexample, Cu and CuSe, which are impurities, and excessive Se can easilybe separated and removed from polycrystal particles (e.g. CdSe and ZnS)which are raw materials being subjected to the polish-pulverization.

Although there is no especial limitation on the method for carrying outthe above polish-pulverization, yet specific favorable examples thereofinclude methods that involve using various apparatuses that can giveshear force, such as a method that involves using a ball mill(ball-milling method), a method that involves using a sand mill, and amethod that involves using a jet mill. Of the above, the ball-millingmethod is favorable from the viewpoint such that: this method enablesuniform preparation of a nano-sized level of particles having particlediameters of smaller than 1 μm and is excellent in economy andproductivity and is simple.

In the polish-pulverization by the ball-milling method, balls for thepolish-pulverization are usually used. Examples of the balls for thepolish-pulverization include: metal balls made of such as stainlesssteel and titanium; ceramic balls made of such as alumina, silica, andzirconia; and glass balls (glass beads) made of such as glass.

In addition, although not especially limited, the particle diameters ofthe balls for the polish-pulverization are specifically favorably in therange of 0.1 μm to 10 mm. In the case where the particle diameters aresmaller than 0.1 μm, there is a possibility that the use of only theseballs for the polish-pulverization may involve a very longpolish-pulverization time, so that the productivity may be deteriorated.In the case where the particle diameters are larger than 10 mm, there isa possibility that the use of only these balls for thepolish-pulverization cannot polish-pulverize the coarse particles of thecompound semiconductor to smaller than 1 μm.

Although there is no especial limitation on the mixing amount of theballs for the polish-pulverization and the coarse particles of thecompound semiconductor, yet, specifically for example, the amount of theballs for the polish-pulverization as used is favorably in the range of100 to 10,000 parts by weight per 100 parts by weight of the coarseparticles of the compound semiconductor. In the case where the amount issmaller than 100 parts by weight, there is a possibility that the coarseparticles of the compound semiconductor cannot be polish-pulverized tosmaller than 1 μm. In the case where the amount is larger than 10,000parts by weight, there is a possibility that the yield of the compoundsemiconductor particles per pot may be so low as to deteriorate theproductivity.

Although not especially limited, the amount of the solvent as usedduring the polish-pulverization is, specifically for example, favorablyin the range of 1 to 10,000 parts by weight per 100 parts by weight ofthe coarse particles of the compound semiconductor. In the case wherethe amount is smaller than 1 part by weight, there is a possibility thatthe solvent effects (such that the polish-pulverization can efficientlybe carried out) cannot be obtained. In the case where the amount islarger than 10,000 parts by weight, there is a possibility that thepolish-pulverization efficiency may rather be low.

As to the shape of the pot as used for the ball-milling method, anyshape can be adopted and is therefore not especial limited. However,there is usually used a columnar container. The bottom of the pot may bea flat face. However, in the case where an angular portion is formed bythe bottom and side of the pot, there is a possibility that the rawmaterials to be polish-pulverized and the polish-pulverized particlesmay stagnate around this angular portion, thus resulting in a low yieldof the polish-pulverization and a broad particle diameter distributionof the particles as obtained. Therefore, the above angular portion isfavorably of the curved shape as formed by removing the angular shape,and the bottom itself is also more favorably a curved face being convexoutward of the pot.

Generally as to the ball-milling method, the pot having such as thecolumnar shape, in which such as the raw materials, the balls for thepolish-pulverization, and the solvent are charged, is set in such amanner that the direction vertical to the circular cross section will behorizontal, and then the pot is revolved around its horizontal axis(revolution of the pot) to thereby pulverize the raw materials by thedropping and rubbing of the above balls. However, this pot may furtherbe set on a revolvable disk to carry out the treatment in combination ofthe aforementioned revolution of the pot and the revolution of thisdisk. Besides, modes such as a shaker method are favorably cited forexample.

In the ball-milling method, there is no especial limitation on therevolution rate of the above pot, but the revolution rate will do if itis fitly set so that there can be obtained the compound semiconductorparticles having particle diameters of smaller than 1 μm. However, forexample, the revolution rate is favorable in the range of 60 to 10,000rpm. In the case where the revolution rate is less than 60 rpm, there isa possibility that the polish-pulverization efficiency may be low. Inthe case where the revolution rate is more than 10,000 rpm, there is apossibility that the polish-pulverized particles may re-aggregate orfuse together to make it difficult to obtain the particles havingparticle diameters of smaller than 1 μm.

In addition, in the case of also carrying out the above revolution ofthe disk in combination, the revolution rate of this disk is notespecially limited, either. The revolution rate will do if it is fitlyset so that there can be obtained the compound semiconductor particleshaving particle diameters of smaller than 1 μm. However, for example,the revolution rate is favorable in the range of 6 to 10,000 rpm. In thecase where the revolution rate is less than 6 rpm, there is apossibility that the effects of the revolution of the disk cannot beobtained. In the case where the revolution rate is more than 10,000 rpm,there is a possibility that the centrifugal force may be too strong,thus resulting in rather a low polish-pulverization efficiency.

The polish-pulverization time in the ball-milling method will do if itis fitly set according to the size and amount of the coarse particles ofthe compound semiconductor being used as a raw material, and besides,according to operational conditions of the above various ball mills, sothat there can be obtained the compound semiconductor particles havingparticle diameters of smaller than 1 μm. Thus, there is no especiallimitation. However, for example, the time is favorably in the range of0.1 to 100 hours.

In the ball-milling method, the balls for the polish-pulverization canbe used in at least two kinds different as to their particle diametersand materials. During the polish-pulverization, different kinds of ballsmay be used at the same time, or the balls may be used while the kindsof the balls are changed stepwise. For example, if at least two kinds ofballs for the polish-pulverization different as to such as theirparticle diameters are fitly selected and used according to the particlediameters of the objective compound semiconductor particles and/or thesize of the coarse particles of the compound semiconductor particles,then particles having desired particle diameters can uniformly beobtained more efficiently. Particularly in the case where particleshaving smaller particle diameters are intended to be obtained easily,uniformly, and efficiently, it is favorable to fitly select and use atleast two kinds of balls for the polish-pulverization different as tosuch as their particle diameters.

In the present invention, the heat-treatment may be carried out at atemperature of not lower than 50° C. after the polish-pulverization. Inaddition, the heat-treatment may be carried out at a temperature of notlower than 50° C. after the surface-covering treatment.

The body particles in the compound semiconductor particles according tothe present invention will do if the contents, resultant from thepolish-pulverization, of the pot are, for example, filtrated to therebyseparate and take out the fined compound semiconductor particles fromthe coarse particles. In detail, it is favorable that: the balls for thepolish-pulverization are first separated from the contents, resultantfrom the polish-pulverization, of the pot, and thereafter the compoundsemiconductor particles are separated.

The body particles in the compound semiconductor particles according tothe present invention are obtained as compound semiconductor particleshaving particle diameters of smaller than 1 μm, more favorably notlarger than 0.1 μm, more favorably not larger than 0.01 μm.

Although not especially limited, the uses of the body particles in thecompound semiconductor particles according to the present invention are,for example, favorably the same as mentioned as the uses of the abovecompound semiconductor particles according to the present invention. Inaddition, it is also possible that the body particles in the compoundsemiconductor particles according to the present invention are used asthe body particles of the compound semiconductor particles as coveredwith such as the metal oxide.

The monodispersibility of the compound semiconductor particles accordingto the present invention is favorably not more than 20, more favorablynot more than 10, still more favorably not more than 5. In the casewhere the above monodispersibility is more than 20, for example, thereis a possibility that the functions peculiar to the metal-oxide-coveredparticles may be displayed insufficiently due to the light-scatteringeffect caused by the aggregation and also due to the formation of a filmin which the particles are non-uniformly dispersed when the particlesget contained in a film.

The monodispersibility is shown by the ratio of dispersed-particlediameter/primary-particle diameter, wherein the primary-particlediameter is the average particle diameter of not aggregated singleparticles as determined from their TEM image (number of particlesmeasured: 50).

[Production Process for Compound Semiconductor Particles]:

The first production process for compound semiconductor particles,according to the present invention, is characterized by comprising thestep of heating and/or polish-pulverizing a mixture including a metalcarboxylate, an alcohol, and particles or a mixture including ametal-alkoxy-group-containing compound, a carboxyl-group-containingcompound, and particles, thereby covering the particles with a metaloxide, wherein the particles include a compound semiconductor.

In the first production process, the metal oxide covering the particlesincluding the compound semiconductor can be formed by heating and/orpolish-pulverizing the mixture including the metal carboxylate, thealcohol, and the particles or the mixture including themetal-alkoxy-group-containing compound, the carboxyl-group-containingcompound, and the particles (wherein the particles include the compoundsemiconductor) to thereby run a heat reaction between the metalcarboxylate and the alcohol (hereinafter this reaction may be referredto as “first reaction”) or a heat reaction between themetal-alkoxy-group-containing compound and the carboxyl-group-containingcompound (hereinafter this reaction may be referred to as “secondreaction”). In detail, this heat reaction is run by heat as positivelyapplied to the aforementioned mixture and/or by frictional heat asgenerated with the polish-pulverization of the aforementioned mixture(namely, the polish-pulverization of the particles including thecompound semiconductor in the aforementioned mixture), whereby the metaloxide can be formed. If the heat reaction between the metal carboxylateand the alcohol or the heat reaction between themetal-alkoxy-group-containing compound and the carboxyl-group-containingcompound is carried out in the presence of the particles including thecompound semiconductor in this way, then the particles including thecompound semiconductor can be covered with the metal oxide with economy,good productivity, and ease.

Hereinafter, the components that can be contained in the above mixtureare explained.

Preferred examples of the compound semiconductor constituting the aboveparticles including the compound semiconductor include the same asmentioned in the explanation of the above compound semiconductorparticles according to the present invention.

Although there is no especial limitation on the shape of the aboveparticles including the compound semiconductor, yet examples thereofinclude a spherical shape, a sheet shape, a needle shape, a columnarshape, and an irregular shape. Particles having a uniform shape and/or auniform size are favorable.

In addition, the particle diameters of the above particles including thecompound semiconductor will do if there are used particles as fitlyprepared in such a manner that the particle diameters will be almost thesame as those of the resulting compound semiconductor particles inconsideration of such as uses of the resulting compound semiconductorparticles. Although not especially limited, the particle diameters arefavorably smaller than 1 μm, more favorably smaller than 0.1 μm, stillmore favorably smaller than 0.02 μm. The particle diameters to producethe quantum effects differ depending upon the kinds of the rawsubstances. However, generally, if the particles are in the nano-sizedrange such that the particle diameters are smaller than 1 μm, then thesame effects as mentioned, in the explanation of the above presentinvention compound semiconductor particles can be obtained due to thequantum effects. For example, such as the luminescence property can beenhanced more. Incidentally, the above particles including the compoundsemiconductor can be prepared by applying hitherto publicly knownproduction techniques for compound semiconductor particles.

Although there is no especial limitation on the metal carboxylate asused in the first reaction, yet examples thereof include metal salts ofvarious carboxyl-group-containing compounds as hitherto publicly known.Among these, metal saturated-carboxylates are favorable, and metalacetates are the most favorable. Although there is no especiallimitation on the metal (M′) contained in the metal carboxylate either,yet it is favorable that the M′ is a metal element belonging to such asgroup 1A, group 2A, group 3A, group 4A, group SA, group 6A, group 7A,group 8, lanthanoide elements, group 1B, group 2B, group 3B, group 4B,group 5B, or group 6B in the periodic table. Among these, metal elementsthat can form oxides having no light absorption in the visible range(e.g. Zn, Al, In, Si, Sn, Sb, Y, La, Mg, Ca, Sr, and Ba) are useful andfavorable.

The above metal carboxylates may be used either alone respectively or incombinations with each other.

Although there is no especial limitation on the alcohol as used in thefirst reaction, yet examples thereof include: monohydric alcohols, suchas aliphatic monohydric alcohols (e.g. methanol, ethanol, isopropylalcohol, n-butanol, t-butyl alcohol, and stearyl alcohol), unsaturatedaliphatic monohydric alcohols (e.g. allyl alcohol, crotyl alcohol, andpropargyl alcohol), alicyclic monohydric alcohols (e.g. cyclopentanoland cyclohexanol), aromatic monohydric alcohols (e.g. benzyl alcohol,cinnamyl alcohol, and methylphenylcarbinol), phenols (e.g. ethylphenol,octylphenol, catechol, xylenol, guaiacol, p-cumylphenol, cresol,m-cresol, o-cresol, p-cresol, dodecylphenol, naphthol, nonylphenol,phenol, benzylphenol, and p-methoxyethylphenol), and heterocyclicmonohydric alcohols (e.g. furfuryl alcohol); glycols, such as alkyleneglycols (e.g. ethylene glycol, propylene glycol, trimethylene glycol,1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol,1,10-decanediol, pinacol, diethylene glycol, and triethylene glycol),aromatic-ring-containing aliphatic glycols (e.g. hydrobenzoin,benzpinacol, and phthallyl alcohol), alicyclic glycols (e.g.cyclopentane-1,2-diol, cyclohexane-1,2-diol, and cyclohexane-1,4-diol),and polyoxyalkylene glycols (e.g. polyethylene glycol and polypropyleneglycol); derivatives, such as monoethers and monoesters, of the aboveglycols (e.g. propylene glycol monomethyl ether, propylene glycolmonoethyl ether, dipropylene glycol monomethyl ether, tripropyleneglycol monomethyl ether, 3-methyl-3-methoxybutanol, ethylene glycolmonoethyl ether, ethylene glycol monobutyl ether, triethylene glycolmonomethyl ether, and ethylene glycol monoacetate); aromatic diols andtheir monoethers and monoesters (e.g. hydroquinone, resorcin, and2,2-bis(4-hydroxyphenyl)propane); and trihydric alcohols (e.g. glycerin)and their monoethers, monoesters, diethers, and diesters.

The above alcohols may be used either alone respectively or incombinations with each other.

Although not especially limited, the mixing mount of the alcohol as usedin the first reaction is favorably in the range of 1 to 1,000 times,more favorably 2 to 100 times, particularly favorably 5 to 50 times, inmolar ratio to the content of the metal of the above metal carboxylate.

The metal-alkoxy-group-containing compound as used in the secondreaction is not especially limited. However, examples thereof include:compounds shown by the following general formula (1); and their(partially) hydrolyzed and condensed products.M(OR^(a))_(n-m)R^(b) _(m)   (1)(wherein: M is a metal atom; R^(a) is at least one species selected fromamong a hydrogen atom, alkyl groups, cycloalkyl groups, acyl groups,aralkyl groups, and aryl groups (wherein these groups may have asubstituent); R^(b) is at least one species selected from among ahydrogen atom, alkyl groups, cycloalkyl groups, acyl groups, aralkylgroups, aryl groups, unsaturated aliphatic residues, and organic groupscontaining functional groups other than the OR^(a) groups (wherein thesegroups may have a substituent); n is the valence of the metal atom M;and m is an integer in the range of 0 to n-1).

In the general formula (1), R^(a) is favorably a hydrogen atom and/or analkyl group which may have a substituent, such as an alkoxyalkyl group.In addition, R^(b) is favorably at least one species selected from amongalkyl groups, cycloalkyl groups, acyl groups, aralkyl groups, arylgroups, unsaturated aliphatic residues, and organic groups containingfunctional groups other than the OR^(a) groups such as β-diketonecompounds (wherein these groups may have a substituent).

In the general formula (1), examples of M include the metals ascontained in the above metal carboxylates, and preferable examples of Malso include the same as those of the metals as contained in the abovemetal carboxylates.

In the general formula (1), examples of metal-alkoxy-group-containingcompounds of m=1, 2 or 3 include a variety of: organosilicon compounds(m=1, 2 or 3), titanate type coupling agents (m=1, 2 or 3), andaluminate type coupling agents (m=1 or 2).

Examples of the organosilicon compounds include: vinyl type silanecoupling agents such as vinyltrimethoxysilane, vinyltriethoxysilane,vinyltris(β-methoxyethoxy)silane, and vinyltriacetoxysilane; amino typesilane coupling agents such asN-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane,3-N-phenyl-γ-aminopropyltrimethoxysilane, andN,N′-bis[3-(trimethoxysilyl)propyl]ethylenediamine; epoxy type silanecoupling agents such as γ-glycidoxypropyltrimethoxysilane andβ-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; chloro type silanecoupling agents such as 3-chloropropyltrimethoxysilane; methacryloxytype silane coupling agents such as3-methacryloxypropyltrimethoxysilane; mercapto type silane couplingagents such as 3-mercaptopropyltrimethoxysilane; ketimine type silanecoupling agents such asN-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine; cationicsilane coupling agents such asN-[2-(vinylbenzylamino)ethyl]-3-aminopropyltrimethoxysilanehydrochloride; alkyl type silane coupling agents such asmethyltrimethoxysilane, trimethylmethoxysilane, decyltriethoxysilane,and hydroxyethyltrimethoxysilane; and γ-ureidopropyltriethoxysilane.

Examples of the titanate type coupling agents includeisopropyltriisostearoyl titanate, isopropyltrioctanoyl titanate,tetraoctylbis(ditridecylphosphite)titanate,tetraisopropylbis(dioctylphosphite)titanate,tetraisopropyltris(dioctylpyrophosphate)titanate,bis(dioctylpyrophosphate)oxyacetate titanate,bis(dioctylpyrophosphate)ethylene titanate,isopropyltri(dioctylphosphate)titanate,isopropyltri(N-aminoethyl-aminoethyl)titanate,tetra(2,2-diallyloxymethyl-1-butyl)bis(ditridecyl)phosphite titanate,isopropyldimethacrylisostearoyl titanate,isopropyltridecylbenzenesulfonyl titanate, and isopropyltricumylphenyltitanate.

Examples of the aluminate type coupling agents includediisopropoxyaluminum ethylacetoacetate, diisopropoxyaluminumalkylacetoacetates, diisopropoxyaluminum monomethacrylate,isopropoxyaluminum alkylacetoacetate mono(dioctylphosphate), and cyclicaluminum oxide isopropylate.

The metal-alkoxy-group-containing compound may be other than theabove-explained ones. Examples thereof may include: metal alkoxidecompounds of m=0 in the general formula (1), such as tetramethoxysilane,tetra-n-butoxysilane, tetra-n-butoxytitanium, tri-n-butoxyaluminum,tetraisopropoxytin, and indium trimethoxyethoxide; andheterometal-alkoxy-group-containing compounds (also includingheterometal-oxoalkoxy-group-containing compounds). Incidentally, theheterometal-alkoxy-group-containing compounds refer tometal-alkoxy-group-containing compounds which have at least twodifferent metal atoms that are bonded to each other through an alkoxygroup or oxygen atom or through such as metal-metal bonding. In the casewhere the heterometal-alkoxy-group-containing compounds are used, metaloxides including composite oxides can be obtained.

The above metal-alkoxy-group-containing compounds may be used eitheralone respectively or in combinations with each other.

There is no especial limitation on the carboxyl-group-containingcompound used in the second reaction, if it is a compound having atleast one carboxyl group in its molecule. Examples thereof include:chain carboxylic acids such as saturated fatty acids (saturatedmonocarboxylic acids) (e.g. formic acid, acetic acid, propionic acid,isobutyric acid, caproic acid, caprylic acid, lauric acid, myristicacid, palmitic acid, and stearic acid), unsaturated fatty acids(unsaturated monocarboxylic acids) (e.g. acrylic acid, methacrylic acid,crotonic acid, oleic acid, and linolenic acid), saturated polycarboxylicacids (e.g. oxalic acid, malonic acid, succinic acid, adipic acid,suberic acid, and β,β-dimethylglutaric acid), and unsaturatedpolycarboxylic acids (e.g. maleic acid and fumaric acid); cyclicsaturated carboxylic acids such as cyclohexanecarboxylic acid; aromaticcarboxylic acids such as aromatic monocarboxylic acids (e.g. benzoicacid, phenylacetic acid, and toluic acid) and unsaturated polycarboxylicacids (e.g. phthalic acid, isophthalic acid, terephthalic acid,pyromellitic acid, and trimellitic acid); carboxylic anhydrides such asacetic anhydride, maleic anhydride, and pyromellitic anhydride;compounds having another functional or atomic group (e.g. a hydroxylgroup, an amino group, a nitro group, an alkoxy group, a sulfonic acidgroup, a cyano group, a halogen atom) besides the carboxyl group intheir molecules, such as trifluoroacetic acid, o-chlorobenzoic acid,o-nitrobenzoic acid, anthranilic acid, p-aminobenzoic acid, anisic acid(p-methoxybenzoic acid), toluic acid, lactic acid, and salicylic acid(o-hydroxybenzoic acid); and polymers of which the starting materialsinclude at least one of the above unsaturated carboxylic acids, such ashomopolymer of acrylic acid and copolymer of acrylic acid and methylmethacrylate. Of these carboxyl-group-containing compounds, thesaturated carboxylic acids are favorable, and acetic acid is the mostfavorable, for obtaining particles having excellent dispersibility. Inaddition, in the case where the carboxyl-group-containing compound isliquid, it is also possible to use this compound also as thebelow-mentioned reaction solvent.

The above carboxyl-group-containing compounds may be used either alonerespectively or in combinations with each other.

As to the carboxyl-group-containing compound used in the secondreaction, there is no especial limitation on the mixing ratio betweenthe metal-alkoxy-group-containing compound and thecarboxyl-group-containing compound (metal-alkoxy-group-containingcompound/carboxyl-group-containing compound). However, the lower limitof the above mixing ratio is favorably more than 0.8 n, more favorablymore than 2 n, and also the upper limit of the above mixing ratio isfavorably less than 10 n, wherein “n” is the valence of the metal atom Mas contained in the metal-alkoxy-group-containing compound.

In the production process according to the present invention, themixture including the metal carboxylate, the alcohol, and the particlesor the mixture including the metal-alkoxy-group-containing compound, thecarboxyl-group-containing compound, and the particles (wherein theparticles include the compound semiconductor) may further include suchas a reaction solvent.

There is no especial limitation on the amount of the reaction solvent asused. However, in the mixture including the metal carboxylate, thealcohol, and particles (wherein the particles include the compoundsemiconductor), the amount of the reaction solvent as used is favorablyset in such a manner that the concentration of the metal carboxylatewill be in the range of 1 to 50 weight % relative to the total of themetal carboxylate, the alcohol, and the reaction solvent. In addition,in the mixture including the metal-alkoxy-group-containing compound, thecarboxyl-group-containing compound, and the particles (wherein theparticles include the compound semiconductor), the amount of thereaction solvent as used is favorably set in such a manner that theconcentration of the metal-alkoxy-group-containing compound will be inthe range of 1 to 50 weight % relative to the total of themetal-alkoxy-group-containing compound, the carboxyl-group-containingcompound, and the reaction solvent. Thereby, the compound semiconductorparticles as covered with the metal oxide can be obtained economically.

As to the reaction solvent, solvents other than water, in other words,non-aqueous solvents, are favorable. Examples of the non-aqueoussolvents include: hydrocarbons; halogenated hydrocarbons; alcohols (alsoincluding such as phenols, polyhydric alcohols, and their derivativeswhich are hydroxyl-group-containing compounds); ethers and acetals;ketones and aldehydes; esters; derivative compounds as formed bydisplacement of active hydrogen atoms of all hydroxyl groups of thepolyhydric alcohols with an alkyl group and/or an acetoxy group;carboxylic acids and their anhydrides; silicone oils; and mineral oils.

Examples of the above hydrocarbons include amylbenzene,isopropylbenzene, ethylbenzene, octane, gasoline, xylenes,diethylbenzene, cyclohexane, cyclohexylbenzene, cyclohexene,cyclopentane, dimethylnaphthalene, cymenes, camphor oil, styrene,petroleum ether, petroleum benzine, solvent naphtha, decalin, decane,tetralin, turpentine oil, kerosine, dodecane, dodecylbenzene, toluene,naphthalene, nonane, pine oil, pinene, biphenyl, butane, propane,hexane, heptane, benzene, pentane, mesitylene, methylcyclohexane,methylcyclopentane, p-menthane, ligroin, and liquid paraffin.

Examples of the above halogenated hydrocarbons include allyl chloride,2-ethylhexyl chloride, amyl chloride, isopropyl chloride, ethylchloride, chlorinated naphthalenes, butyl chloride, hexyl chloride,methyl chloride, methylene chloride, o-chlorotoluene, p-chlorotoluene,chlorobenzene, chloroform, carbon tetrachloride, 1,1-dichloroethane,1,2-dichloroethane, 1,1-dichloroethylene, 1,2-dichloroethylene,2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene,2,6-dichlorotoluene, 3,4-dichlorotoluene, 3,5-dichlorotoluene,dichlorobutanes, dichloropropane, m-dichlorobenzene, o-dichlorobenzene,p-dichlorobenzene, dibromoethane, dibromobutane, dibromopropane,dibromobenzene, dibromopentane, allyl bromide, isopropyl bromide, ethylbromide, octyl bromide, butyl bromide, propyl bromide, methyl bromide,lauryl bromide, 1,1,1,2-tetrachloroethane, 1,1,2,2-tetrachloroethane,tetrachloroethylene, tetrabromoethane, tetramethylene chlorobromide,1,1,1-trichloroethane, 1,1,2-trichloroethane, trichloroethylene,1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene,bromochloroethane, 1-bromo-3-chloropropane, bromonaphthalene,hexachloroethane, and pentamethylene chlorobromide.

Preferred examples of the above alcohols (including phenols, polyhydricalcohols, and their derivatives which are hydroxyl-group-containingcompounds) include the same as enumerated as examples of the alcoholcontained in the above mixture.

Examples of the above ethers and acetals include anisole, ethyl isoamylether, ethyl t-butyl ether, ethyl benzyl ether, epichlorohydrin,epoxybutane, crown ethers, cresyl methyl ether, propylene oxide,diisoamyl ether, diisopropyl ether, diethyl acetal, diethyl ether,dioxane, diglycidyl ether, 1,8-cineol, diphenyl ether, dibutyl ether,dipropyl ether, dibenzyl ether, dimethyl ether, tetrahydropyran,tetrahydrobifuran, trioxane, bis(2-chloroethyl)ether, vinyl ethyl ether,vinyl methyl ether, phenetole, butyl phenyl ether, furan, furfural,methylal, methyl t-butyl ether, methylfuran, and monochlorodiethylether.

Examples of the above ketones and aldehydes include acrolein,acetylacetone, acetaldehyde, acetophenone, acetone, isophorone, ethyln-butyl ketone, diacetone alcohol, diisobutyl ketone, diisopropylketone, diethyl ketone, cyclohexanone, di-n-propyl ketone, phorone,mesityl oxide, methyl n-amyl ketone, methyl isobutyl ketone, methylethyl ketone, methylcyclohexanone, methyl n-butyl ketone, methyln-propyl ketone, methyl n-hexyl ketone, and methyl n-heptyl ketone.

Examples of the above esters include diethyl adipate, dioctyl adipate,triethyl acetylcitrate, tributyl acetylcitrate, allyl acetoacetate,ethyl acetoacetate, methyl acetoacetate, methyl abietate, isoamylbenzoate, ethyl benzoate, butyl benzoate, propyl benzoate, benzylbenzoate, methyl benzoate, isoamyl isovalerate, ethyl isovalerate,isoamyl formate, isobutyl formate, ethyl formate, butyl formate, propylformate, hexyl formate, benzyl formate, methyl formate, tributylcitrate, ethyl cinnamate, methyl cinnamate, amyl acetate, isoamylacetate, isobutyl acetate, isopropyl acetate, ethyl acetate,2-ethylhexyl acetate, cyclohexyl acetate, n-butyl acetate, s-butylacetate, propyl acetate, benzyl acetate, methyl acetate,methylcyclohexyl acetate, isoamyl salicylate, benzyl salicylate, methylsalicylate, diamyl oxalate, diemyl oxalate, dibutyl oxalate, diethyltartarate, dibutyl tartarate, amyl stearate, ethyl stearate, butylstearate, dioctyl sebacate, dibutyl sebacate, diethyl carbonate,diphenyl carbonate, dimethyl carbonate, amyl lactate, ethyl lactate,butyl lactate, methyl lactate, diethyl phthalate, dioctyl phthalate,dibutyl phthalate, dimethyl phthalate, γ-butyrolactone, isoamylpropionate, ethyl propionate, butyl propionate, benzyl propionate,methyl propionate, borate esters, dioctyl maleate, diisopropyl maleate,diethyl malonate, dimethyl malonate, isoamyl butyrate, isopropylbutyrate, ethyl butyrate, butyl butyrate, methyl butyrate, and phosphateesters.

Examples of the above derivative compounds, as formed by displacement ofactive hydrogen atoms of all hydroxyl groups of the polyhydric alcoholswith an alkyl group and/or an acetoxy group, include ethylene carbonate,ethylene glycol diacetate, ethylene glycol diethyl ether, ethyleneglycol diglycidyl ether, ethylene glycol dibutyl ether, ethylene glycoldimethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycolmonobutyl ether acetate, diethylene glycol ethyl methyl ether,diethylene glycol diacetate, diethylene glycol diethyl ether, diethyleneglycol dibutyl ether, diethylene glycol dibenzoate, diethylene glycoldimethyl ether, diethylene glycol monoethyl ether acetate, diethyleneglycol monobutyl ether acetate, triethylene glycol di-2-ethylbutyrate,triethylene glycol dimethyl ether, polyethylene glycol fatty aciddiesters, poly(oxyethylene)derivatives containing no hydroxyl group atboth ends, and poly(oxypropylene)derivatives containing no hydroxylgroup at both ends.

In the case where the compound semiconductor particles are produced byutilizing the first reaction in the first production process accordingto the present invention, the amount of the metal carboxylate as used isfavorably in the range of 10 to 10,000 parts by weight per 100 parts byweight of the particles including the compound semiconductor. In thecase where the amount is smaller than 10 parts by weight, there is apossibility that the particles including the compound semiconductor maynot be covered with the metal oxide to such an extent that the coveringeffects can sufficiently be obtained. In the case where the amount islarger than 10,000 parts by weight, there is a possibility that: theparticles including the compound semiconductor may be covered with themetal oxide which is thicker than is necessary, or much of the metaloxide may be formed in the form of such as particles without beingprovided to the covering.

In the case where the compound semiconductor particles are produced byutilizing the second reaction in the first production process accordingto the present invention, the amount of themetal-alkoxy-group-containing compound as used is favorably in the rangeof 10 to 10,000 parts by weight per 100 parts by weight of the particlesincluding the compound semiconductor. If the amount of themetal-alkoxy-group-containing compound as used is set so as to satisfythe above range, then the covering with the metal oxide is easily madeupon surfaces of the particles including the compound semiconductor, andbesides, the particles are covered with a crystalline metal oxide, sothat the effects by the covering can sufficiently be obtained. Inaddition, in the case where the amount of themetal-alkoxy-group-containing compound as used is smaller than 10 partsby weight per 100 parts by weight of the particles including thecompound semiconductor, there is a possibility that the covering withthe metal oxide may be difficult to make uniformly throughout the entiresurface of the particle including the compound semiconductor, and thereis a possibility that, even if the covering is not made throughout theentire surface, the covering may not be made with a uniformdistribution. Besides, there are disadvantages in that the covering withthe crystalline metal oxide is difficult to make. In addition, in thecase where the amount of the metal-alkoxy-group-containing compound asused is larger than 10,000 parts by weight per 100 parts by weight ofthe particles including the compound semiconductor, there is apossibility that: the particles including the compound semiconductor maybe covered with the metal oxide which is thicker than is necessary, ormuch of the metal oxide may be formed in the form of such as particleswithout being provided to the covering.

In the first production process according to the present invention, itis favorable that the metal compound provided to the covering is a metaloxide to which the acyloxyl group is bonded. If the metal oxide to whichthe acyloxyl group is bonded is provided to the covering, then there canfurther be enhanced various effects due to the covering with the metaloxide, particularly, the dispersibility into various mediums. Examplesof the acyloxyl group include an acetoxy group (ethanoyloxy group), apropionyloxy group, and an 2-ethylhexanoyloxy group. However, above all,the acetoxy group (ethanoyloxy group) is particularly favorable.

Hereinafter, more detailed explanations are made about the heating ofthe mixture including the metal carboxylate, the alcohol, and theparticles including the compound semiconductor or the mixture includingthe metal-alkoxy-group-containing compound, thecarboxyl-group-containing compound, and the particles including thecompound semiconductor (the first production process by the heating).Thereafter, explanations are made also about the polish-pulverization ofthe above mixture (the first production process by thepolish-pulverization).

In the first production process by the heating, when the first or secondreaction is utilized, the heating temperature is usually favorably notlower than 50° C. And, more favorably for shortening the time to obtainthe compound semiconductor particles as covered with the metal oxide,the heating temperature is not lower than 100° C. In addition, stillmore favorably for suppressing the cohesion between the coveredparticles as obtained, the heating temperature is not higher than 300°C.

In the first production process by the heating, the lower water contentin the above mixture is preferable in that the compound semiconductorparticles are more easily covered with the metal oxide. Specifically,the amount of water as contained (water content) in the above mixture isfavorably so slight as to be less than 4, more favorably less than 1,still more favorably less than 0.2, particularly favorably less than0.1, in molar ratio to the metal atom of the metal carboxylate containedin the above mixture or to the metal atom of themetal-alkoxy-group-containing compound contained in the above mixture.

The first production process by the heating may be carried out under anypressure selected from among normal pressure, applied pressure, andreduced pressure. In the case where the boiling point of such as thereaction solvent is lower than the reaction temperature, that will do ifthe reaction is carried out with a pressure-resistant reactionapparatus. Usually, the reaction is carried out in such a manner thatthe reaction temperature and the gas phase pressure during the reactionare not higher than the critical points of the solvent. However, it isalso possible that the reaction is carried out under super-criticalconditions.

Hereinafter, the specific operational procedure for carrying out thefirst production process by the heating is explained by classifying itinto a case utilizing the first reaction and a case utilizing the secondreaction.

Although there is no especial limitation on the specific operationalprocedure in the case utilizing the first reaction, yet examples thereofinclude: (1a) a method including the steps of preparing the mixtureincluding the metal carboxylate, the alcohol, and the particlesincluding the compound semiconductor, and then heating this mixture toraise its temperature; (2a) a method including the step of mixing theheated alcohol with the metal carboxylate and the particles includingthe compound semiconductor; (3a) a method including the step of mixingthe heated alcohol and the heated particles including the compoundsemiconductor with the metal carboxylate; (4a) a method including thesteps of heating the reaction solvent and the metal carboxylate, andthereafter mixing them with the alcohol and the particles including thecompound semiconductor; (5a) a method including the steps of heating thereaction solvent, the metal carboxylate, and the particles including thecompound semiconductor, and thereafter mixing them with the alcohol; and(6a) a method including the step of mixing the components, which canconstitute the mixture and are in a heated state, and the particlesincluding the compound semiconductor together. In addition, in the abovemethods (3a) and (5a), the metal carboxylate in the case of the method(3a) and the alcohol in the case of the method (5a) are little by littlepulsewise added or slowly fed-added favorably for gradually making theformation of a covering film by the metal oxide to form a uniform metaloxide layer on surfaces of the particles including the compoundsemiconductor.

In the case utilizing the first reaction, it is favorable to use themethods (3a) and (5a), more favorably the method (3a), among the aboveoperational procedures. By these methods, the individual singleparticles including the compound semiconductor can sufficiently becovered with the metal oxide uniformly and efficiently. As is mentionedabove, when the method (3a) is carried out, it is favorable to mix (add)the metal carboxylate by the continuous feed or the pulse addition.However, the addition rate of the metal carboxylate is favorably notmore than 0.5 part/minute, more favorably 0.2 part/minute, in terms ofmetal oxide per 1 part by weight of the particles including the compoundsemiconductor. In the case where the above addition rate is more than0.5 part/minute, there is a possibility that the ratio of the coveringupon the particles including the compound semiconductor may be so lowthat fine particles of the metal oxide tend to form alone and mingle.

In the above methods (2a) to (6a), particularly in the method (3a), itis favorable to keep the reaction temperature constant during the mixing(addition) (from the beginning till the end of the mixing (addition)).Specifically, it is favorable to keep the reaction temperature in therange of ±10° C., more favorably ±5° C., still more favorably ±2° C.,around the predetermined reaction temperature. In the case where thevariation of the reaction temperature during the mixing (addition) ismore than ±10° C., there is a possibility that the ratio of the coveringupon the particles including the compound semiconductor may be so lowthat fine particles of the metal oxide tend to form alone and mingle.This is remarkable particularly in the case where the reactiontemperature rises by its variation of more than +10° C.

Although there is no especial limitation on the specific operationalprocedure in the case utilizing the second reaction, yet examplesthereof include: (1b) a method including the steps of preparing themixture including the metal-alkoxy-group-containing compound, thecarboxyl-group-containing compound, and the particles including thecompound semiconductor, and then heating this mixture to raise itstemperature; (2b) a method including the step of mixing the heatedcarboxyl-group-containing compound with themetal-alkoxy-group-containing compound and the particles including thecompound semiconductor; (3b) a method including the step of mixing theheated carboxyl-group-containing compound and the heated particlesincluding the compound semiconductor with themetal-alkoxy-group-containing compound; (4b) a method including thesteps of heating the reaction solvent and themetal-alkoxy-group-containing compound, and thereafter mixing them withthe carboxyl-group-containing compound and the particles including thecompound semiconductor; (5b) a method including the steps of heating thereaction solvent, the metal-alkoxy-group-containing compound, and theparticles including the compound semiconductor, and thereafter mixingthem with the carboxyl-group-containing compound; and (6b) a methodincluding the step of mixing the components, which can constitute themixture and are in a heated state, and the particles including thecompound semiconductor together. Above all, in the above methods (3b)and (5b), the metal-alkoxy-group-containing compound in the case of themethod (3b) and the carboxyl-group-containing compound in the case ofthe method (5b) are little by little pulsewise added or slowlycontinuously fed-added favorably for gradually making the formation of acovering film by the metal oxide to form a uniform metal oxide layer onsurfaces of the particles including the compound semiconductor.

In the case utilizing the second reaction, it is favorable to use themethods (3b) and (5b), more favorably the method (3b), among the aboveoperational procedures. By these methods, the individual singleparticles including the compound semiconductor can sufficiently becovered with the metal oxide uniformly and efficiently. As is mentionedabove, when the method (3b) is carried out, it is favorable to mix (add)the metal-alkoxy-group-containing compound by the continuous feed or thepulse addition in the above way. However, the addition rate of themetal-alkoxy-group-containing compound is favorably not more than 0.5part/minute, more favorably 0.2 part/minute, in terms of metal oxide per1 part by weight of the particles including the compound semiconductor.In the case where the above addition rate is more than 0.5 part/minute,there is a possibility that the ratio of the covering upon the particlesincluding the compound semiconductor may be so low that fine particlesof the metal oxide tend to form alone and mingle.

In the above methods (2b) to (6b), particularly in the method (3b),similarly to the above case utilizing the first reaction, it isfavorable to keep the reaction temperature constant during the mixing(addition) (from the beginning till the end of the mixing (addition)).Specifically, it is favorable to keep the reaction temperature in therange of ±10° C., more favorably ±5° C., still more favorably ±2° C.,around the predetermined reaction temperature. In the case where thevariation of the reaction temperature during the mixing (addition) ismore than ±10° C., there is a possibility that the ratio of the coveringupon the particles including the compound semiconductor may be so lowthat fine particles of the metal oxide tend to form alone and mingle.This is remarkable particularly in the case where the reactiontemperature rises by its variation of more than +10° C.

In the first production process by the polish-pulverization, the mixtureincluding the metal carboxylate, the alcohol, and the particlesincluding the compound semiconductor or the mixture including themetal-alkoxy-group-containing compound, the carboxyl-group-containingcompound, and the particles including the compound semiconductor ispolish-pulverized (specifically, the particles including the compoundsemiconductor in the above mixture are polish-pulverized) so that thefirst or second reaction can be made by heat (thermal energy) asgenerated by the frictional force during this polish-pulverization.Specific examples of methods therefor include: (7a) a method includingthe steps of adding the coarse particles of the compound semiconductorto the mixture including the metal carboxylate and the alcohol (ifnecessary, further including the solvent for the polish-pulverization),and thereafter polish-pulverizing the resultant mixture; and (7b) amethod including the steps of adding the coarse particles of thecompound semiconductor to the mixture including themetal-alkoxy-group-containing compound and the carboxyl-group-containingcompound (if necessary, further including the solvent for thepolish-pulverization), and thereafter polish-pulverizing the resultantmixture. As to various treatment conditions for the polish-pulverizationwhen this first production process by the polish-pulverization iscarried out, there can be favorably applied such as the aforementionedvarious conditions and procedures.

Usually, when the polish-pulverization is carried out such as by theball-milling method, the fractional heat is generated between the ballfor the polish-pulverization or the inner surface of the pot and thesubstance used as a raw material. If the first or second reaction iscarried out by this frictional heat, then particles (favorably,nano-sized particles having particle diameters of smaller than 1 μm) asfined by the polish-pulverization can be obtained, and also, theseparticles can be covered with the metal oxide. Therefore, the abovecovering can economically and extremely easily be carried out. Inaddition, because the surfaces of the compound semiconductor particlescome in a higher energy (temperature) state than the solvent, the firstor second reaction becomes so easy to cause selectively on theaforementioned particle surfaces that: the covering can efficiently becarried out, and besides, the formation of lone particles of the metaloxide can be suppressed, thus resulting also in excellent productivity.

In the first production process according to the present invention, boththe heating and polish-pulverization of the above mixture may be carriedout. The heating and the polish-pulverization may be carried out at thesame time, or the polish-pulverization may be carried out before orafter the heating. For example, while the polish-pulverization iscarried out and while the heat generated by the friction (frictionalheat) is utilized for the first or second reaction, the heating mayfitly further be carried out.

In the case where the heating and the polish-pulverization are carriedout (namely, the heating and the polish-pulverization are carried out atthe same time) in the first production process according to the presentinvention, it is also possible that the above favorable varioustreatment conditions are applied, as they are, to each of the heatingand the polish-pulverization. However, for example, it is favorable alsofor such as economy and productivity that both of them are carried outunder conditions milder than the above favorable various treatmentconditions. These findings can be applied, for example, to the casewhere, while the heat generated by the friction (frictional heat) in thepolish-pulverization is utilized for the first or second reaction, theheating is fitly further carried out.

In the first production process according to the present invention,particles as obtained by a process including the step ofpolish-pulverizing the coarse particles of the compound semiconductor tothereby fine the particles can be used as the particles including thecompound semiconductor that are used as raw materials. If the particlesas beforehand polish-pulverized is used, then, for example, theaforementioned nano-sized level of particles having particle diametersof smaller than 1 μm can be obtained with economy, good productivity,and ease. The above particles as obtained by the polish-pulverizationcan be prepared in the same way as of the polish-pulverization asexplained about the compound semiconductor particles according to thepresent invention.

In the case where the particles as obtained by the polish-pulverizationare used in the first production process by the heating, there can beadopted a method including the steps of: fining the particles by thepolish-pulverization; and thereafter separating and taking out theresultant particles by such as filtration; and thereafter either causingthe particles to exist in the mixture including the metal carboxylateand the alcohol to heat them by such as the above operational procedures(1a) to (6a) or causing the particles to exist in the mixture includingthe metal-alkoxy-group-containing compound and thecarboxyl-group-containing compound to heat them by such as the aboveoperational procedures (1b) to (6b). In addition, in the case where thefirst reaction is used, examples of other methods include: (8a) a methodincluding the steps of carrying out the above polish-pulverization inthe presence of the metal carboxylate (if necessary, the solvent for thepolish-pulverization is also used), and then, after this treatment,adding the alcohol, and then heating the resultant mixture; and (9a) amethod including the steps of carrying out the abovepolish-pulverization in the presence of the alcohol (if necessary, thesolvent for the polish-pulverization is also used), and then, after thistreatment, adding the metal carboxylate, and then heating the resultantmixture. In the case where the second reaction is used, examples ofother methods include: (8b) a method including the steps of carrying outthe above polish-pulverization in the presence of themetal-alkoxy-group-containing compound (if necessary, the solvent forthe polish-pulverization is also used), and then, after this treatment,adding the carboxyl-group-containing compound, and then heating theresultant mixture; and (9b) a method including the steps of carrying outthe above polish-pulverization in the presence of thecarboxyl-group-containing compound (if necessary, the solvent for thepolish-pulverization is also used), and then, after this treatment,adding the metal-alkoxy-group-containing compound, and then heating theresultant mixture.

In the case where the particles as obtained by the polish-pulverizationare used in the first production process by the polish-pulverization,there can be adopted a method including the steps of: fining theparticles by the polish-pulverization; and thereafter separating andtaking out the resultant particles by such as filtration; and thereaftercausing the particles to exist in the mixture including the metalcarboxylate and the alcohol or in the mixture including themetal-alkoxy-group-containing compound and the carboxyl-group-containingcompound to polish-pulverize them by such as the above operationalprocedure (7a) or (7b). In addition, in the case where the firstreaction is used, examples of other methods include: (10a) a methodincluding the steps of polish-pulverizing the coarse particles of thecompound semiconductor in the presence of the metal carboxylate (ifnecessary, the solvent for the polish-pulverization is also used), andthen, or while carrying out the above polish-pulverization, adding thealcohol, and then continuing the polish-pulverization; and (11a) amethod including the steps of polish-pulverizing the coarse particles ofthe compound semiconductor in the presence of the alcohol (if necessary,the solvent for the polish-pulverization is also used), and then, orwhile carrying out the above polish-pulverization, adding the metalcarboxylate, and then continuing the polish-pulverization. In the casewhere the second reaction is used, examples of other methods include:(10b) a method including the steps of polish-pulverizing the coarseparticles of the compound semiconductor in the presence of themetal-alkoxy-group-containing compound (if necessary, the solvent forthe polish-pulverization is also used), and then, or while carrying outthe above polish-pulverization, adding the carboxyl-group-containingcompound, and then continuing the polish-pulverization; and (11b) amethod including the steps of polish-pulverizing the coarse particles ofthe compound semiconductor in the presence of thecarboxyl-group-containing compound (if necessary, the solvent for thepolish-pulverization is also used), and then, or while carrying out theabove polish-pulverization, adding the metal-alkoxy-group-containingcompound, and then continuing the polish-pulverization.

If the above method (10a) or (10b) or the above method (11a) or (11b) iscarried out, then the particles as obtained by the polish-pulverizationcan finally be covered with the metal oxide more uniformly, because thepolish-pulverization is beforehand carried out as the pretreatmentbefore the reaction.

In the first production process according to the present invention, itis intended that the particles including the compound semiconductor canbe covered with the metal oxide in a state where the particles are moredispersed in the form of primary particles. Therefore, it is favorableto carry out the covering reaction in the presence of the aforementionedprimary-particle formation promoter. It is enough that theprimary-particle formation promoter and the particles including thecompound semiconductor are allowed to coexist when or before the heatingand/or polish-pulverization to run the covering reaction is carried out.There is no especial limitation on its method or timing. If the aboveway is carried out, then there can effectively be suppressed theformation of particles such that a secondary aggregate of the particlesincluding the compound semiconductor is covered with the metal oxide,and there can easily be obtained particles such that the particlesincluding the compound semiconductor which are primary particles arecovered with the metal oxide.

In addition, in the first production process by thepolish-pulverization, it is favorable that the particles including thecompound semiconductor is polish-pulverized in the presence of theaforementioned primary-particle formation promoter. It is enough thatthe primary-particle formation promoter and the particles including thecompound semiconductor are allowed to coexist during the abovepolish-pulverization. There is no especial limitation on its method ortiming. As to the particles including the compound semiconductor asfined by the polish-pulverization, the smaller their particle diametersare, the more easily the particles secondarily aggregate again. However,if the above fined particles are obtained in the presence of theprimary-particle formation promoter, then the covering reaction with themetal oxide can be carried out with the above fined particles leftdispersed more in a primary-particle state. As a result, therefore,finer particles as covered with the metal oxide can be obtained easilyin a high yield.

Although not especially limited, the ratio (mixing ratio) of theaforementioned primary-particle formation promoter as added to thecoarse or fine particles of the compound semiconductor to thereby becaused to coexist therewith is, for example, favorably in the range of0.0001 to 1,000 mol % relative to the number of metal atoms contained inthe particles including the compound semiconductor as used. In the casewhere the above mixing ratio is less than 0.0001 mol %, there is apossibility that the dispersing effect due to the dispersing action maynot sufficiently be displayed. In the case where the mixing ratio ismore than 1,000 mol %, the enhancement of the dispersing effect is notseen very much even if the amount as used is more increased, orotherwise there is also a possibility that the dispersing effect may belowered.

In the first production process according to the present invention, itis also possible that surfaces of the resultant compound semiconductorparticles are further treated (secondarily treated) by adding asurface-treating agent to a liquid as obtained by heating and/orpolish-pulverizing the mixture including the metal carboxylate, thealcohol, and the particles including the compound semiconductor or themixture including the metal-alkoxy-group-containing compound, thecarboxyl-group-containing compound, and the particles including thecompound semiconductor. In addition, the surface-treating agent may beadded during the above heating and/or polish-pulverization.

Examples of the surface-treating agent include: various dispersants asenumerated in the above description of the compound semiconductorparticles according to the present invention; and substances aspredetermined for the use for medical markers (surface-treatingsubstances (A)). There is no especial limitation on the amount of thesurface-treating agent as used. This amount will do if it is fitly set.

In the first production process for compound semiconductor particlesaccording to the present invention, the particles including the compoundsemiconductor may be heat-treated at a temperature of not lower than 50°C. before being covered with the metal oxide. Also, the particlesincluding the compound semiconductor may be heat-treated at atemperature of not lower than 50° C. after being covered with the metaloxide. If the particles is heat-treated in these ways, then there is,for example, a case where the properties, particularly the luminescenceproperty, of the resulting compound semiconductor particles areenhanced.

Although not especially limited, the uses of the compound semiconductorparticles as obtained by the first production process according to thepresent invention are favorably the same uses as of the above compoundsemiconductor particles according to the present invention.

The second production process for compound semiconductor particles,according to the present invention, is characterized by comprising thesteps of: polish-pulverizing coarse particles of a compoundsemiconductor to thereby obtain particles having particle diameters ofsmaller than 1 μm (this step may hereinafter be referred to as step(A)); and then covering the resultant particles with a metal oxide (thisstep may hereinafter be referred to as step (B)).

Examples of the aforementioned step (A) include: a step of, in theaforementioned case where the particles as obtained by the processincluding the step of polish-pulverizing the coarse particles of thecompound semiconductor to thereby fine the particles are used as rawmaterials in the first production process according to the presentinvention, carrying out such a process for producing the particles asused as raw materials in the first production process according to thepresent invention; or a step of carrying out a process for obtaining thebody particles of the compound semiconductor particles according to thepresent invention.

There is no especial limitation on the aforementioned step (B), if it isa step of covering the particles (resultant from the step (A)) with themetal oxide. For example, any step is applicable if it is a hithertopublicly known step of carrying out a process for covering the particleswith the metal oxide. However, the step (B) is favorably the step ofcarrying out the covering method as explained about the first productionprocess according to the present invention.

In the second production process for compound semiconductor particlesaccording to the present invention, between the steps (A) and (B) bothexclusive, the particles may be heat-treated at a temperature of notlower than 50° C. (favorably not lower than the boiling point of thesolvent), favorably under pressure. Also, after the aforementioned step(B), the particles may be heat-treated at a temperature of not lowerthan 50° C. (favorably not lower than the boiling point of the solvent),favorably under pressure. If the particles is heat-treated in theseways, then there is, for example, a case where the properties,particularly the luminescence property, of the resulting compoundsemiconductor particles are enhanced.

The present inventors have further found out that the compoundsemiconductor particles according to the present invention or thecompound semiconductor particles as obtained by the first or secondproduction process according to the present invention are very useful asfluophors. Prior fluophors were designed, for such as cathode-ray tubes,fluorescent lamps, and plasma display devices, so that the excitationefficiency would be high in the electron beam range (cathode-ray tubes)and/or in the short wavelength range shorter than 300 nm (fluorescentlamps, plasma display devices). The compound semiconductor particlesaccording to the present invention or the compound semiconductorparticles as obtained by the first or second production processaccording to the present invention are, unlike prior ones, extremelyuseful in point of being usable as fluophors of which the excitationefficiency is high as to long-wavelength ultraviolet rays and/orshort-wavelength visible rays (violet to blue), particularly as to lighthaving a wavelength around 400 nm, specifically, favorably in the rangeof 350 to 450 nm, more favorably 380 to 420 nm.

Examples of uses of the fluophors of which the excitation efficiency ishigh as to the light having a wavelength around 400 nm include: whiteLED; general illumination (substitutes for fluorescent lamps);illumination light sources of LCD (liquid crystal displays);light-emitting diode multicolor displays; tumor markers; andwavelength-converting materials for interior and exterior decorationfilms and for plant-raising films.

Detailed Description of the Preferred Embodiments

Hereinafter, the present invention is more specifically illustrated bythe following examples of some preferred embodiments in comparison withcomparative examples not according to the present invention. However,the present invention is not limited to these examples in any way.Incidentally, for convenience, the units “part(s) by weight”, “liter(s)”and “weight %” may hereinafter be abbreviated simply to “part(s)”, “L”,and “wt %” respectively.

<Preparation of Powder Sample>:

A portion of a dispersion of compound semiconductor particles or aportion of a dispersion of covered compound semiconductor particles wascentrifuged, and the resultant precipitate was washed with acetone andthereafter dried under vacuum at 50° C., thus obtaining the powdersample.

<Average Particle Diameter of Compound Semiconductor Particles as RawMaterials>:

This was determined by measuring the particle diameters of 30 particleswith a scanning electron microscope and number-averaging the measuredparticle diameters.

<Composition (Dopant Concentration and Mixed-Crystal Composition) andCrystal Structure of Compound Semiconductor Particles>:

These were determined by fluorescent X-ray analysis or X-ray powderdiffractometry as to the powder sample and the raw materials.

<Dispersed-Particle Diameter of Polish-Pulverized Compound SemiconductorParticles in its Dispersion>:

This was evaluated with a dynamic light-scattering type particlediameter distribution measurement apparatus (produced by Horiba, Ltd.).In the case where a dilution with a solvent was used as the sample inthe measurement, the same solvent as that in the dispersion was used.

<TEM Particle Diameter of Polish-Pulverized Compound SemiconductorParticles in its Dispersion>:

This was determined by number-averaging the particle diameters of 30primary particles from their transmission-electron-microscopic image.

<Crystal Grain Diameter of Polish-Pulverized Compound SemiconductorParticles in its Dispersion>:

An X-ray powder diffraction pattern of the powder sample was obtainedwith an X-ray powder diffraction apparatus (RINT 2400, produced byRigaku), and then there was measured the full width of the half maximumintensity of a diffraction ray having the highest diffraction intensity(the most intense ray), and then the crystal grain diameter wascalculated from the measured value in accordance with Scherrer equation.In that case, the K value (Scherrer constant) was assumed to be 1.

<Dispersed-Particle Diameter of Covered Compound SemiconductorParticles>:

This was evaluated with a dynamic light-scattering type particlediameter distribution measurement apparatus (produced by Horiba, Ltd.).In the case where a dilution with a solvent was used as the sample inthe measurement, the same solvent as that in the dispersion was used.

<TEM Particle Diameter of Covered Compound Semiconductor Particles>:

This was determined by number-averaging the particle diameters of 30primary particles from their transmission-electron-microscopic image.

<Form of Covered Compound Semiconductor Particles and Form of CoveringLayer>:

They were judged by observation with a transmission electron microscope.

<Film Thickness of Covering Layer of Covered Compound SemiconductorParticles>:

As to any 10 particles, the film thickness was read at 3 portions ofeach particle by observation with a transmission electron microscope.Then, the read film thicknesses at the total 30 portions were averagedto take the resultant average value as the film thickness of thecovering layer.

<Composition of Covering Layer of Covered Compound SemiconductorParticles>:

This was judged from the result of the elemental analysis of thecovering layer portion of the particles and the result of thefluorescent X-ray analysis of the powder sample, wherein the elementalanalysis was carried out while the particles were observed with anFE-TEM (field emission type transmission electron microscope) asequipped with an XMA apparatus (X-ray microanalyzer) having theresolving power of 1 nmφ. In addition, the electron beam diffractometryof the covering layer portion and the X-ray diffractometry of the powdersample were also carried out to thereby confirm whether a crystallinecovering layer was formed or not.

<Bonding Amount of Acyloxyl Group>:

The powder sample was added to a 0.5 N aqueous sodium hydroxide solutionand the resultant mixture was stirred for 24 hours. Thereafter theinsoluble components were removed by centrifugal separation, and theresultant solution was analyzed by ion chromatography, thus determiningthe bonding amount. To make assurance double sure, the pyrolysisproperty of the powder sample was examined by TG-DTA to thereby confirmthe bonding.

<Photoluminescence Property>:

About 50 mg of the powder sample was packed into a measuring portion asformed by boring a hole through a copper plate. Then, the copper platewas fixed to a sample stand of a cryostat and then kept at 10 K undervacuum, and an He—Cd laser (325 nm, excitation intensity: 625 mw/cm²)was used as the excitation source. A high-functional multi-detectionsystem (Multiviewer Macs 320, produced by Jobin Yvon; using the HR-320optical system) was used for the spectroscopy, the detection, and themeasurement.

The luminescence colors were judged from the emission spectrum property.

<Fluorescence Property Due to Light Source of Ultraviolet-Light-EmittingDiode>:

The same apparatus as used for the measurement of the photoluminescenceproperty was used for the spectroscopy, the detection, and themeasurement. An ultraviolet-light-emitting diode (peak wavelength: 400nm) was used as the excitation source.

An amount of 1.5 ml of a dilution of a reaction liquid or dispersion asobtained in each Example was placed as the measurement sample into ameasurement portion including a vial of 1.6 ml in capacity, and then themeasurement was carried out.

Measurement sample: particle concentration=0.5 μg/ml

Diluting solvent: methanol

Measurement conditions: exposing time=2 sec, number of times of delay=5,and number of times of integration=30

Sample temperature during measurement: 25° C. (the sample was adjustedto 25° C. in an isothermal bath of 25° C. in advance of the measurementand thereafter introduced into the measurement portion and immediatelythereafter measured.)

The luminescence colors were judged from the emission spectrum property.

EXAMPLE 1

A stainless-steel (SUS316)-made pot of 120 mL in capacity was chargedwith 270 parts of stainless-steel (SUS316)-made balls having a diameterof 3.18 mmφ (as balls for polish-pulverization), 13 parts of CdSe (asthe compound semiconductor), and 4 parts of heptane (as the solvent),and then the pot was tightly shut. Incidentally, the pot as used was theshape of a column having a sectional diameter of 50 mm, and its bottomhad a curved semispherical face having a radius of curvature of 25 mmand being convex outward of the pot.

This pot was set to a ball mill apparatus to make revolution at a setrevolution rate of the pot of 298 rpm and a set revolution rate of thedisk of 139 rpm for 80 hours, thus carrying out the polish-pulverization(hereinafter referred to as polish-pulverization treatment).

After the polish-pulverization treatment, there was obtained adispersion (1a) of compound semiconductor particles by filtrating thecontents as obtained in the pot. As a result of observation of thedispersion (1a) with a TEM, it was confirmed that CdSe particles havingan average particle diameter of 0.03 μm were formed in the dispersion(1a) wherein a portion of the CdSe particles were fine CdSe particleshaving particle diameters of about 19 nm (as shown in FIG. 1).

Incidentally, the above particle diameters and average particle diameterwere measured by observation with a transmission electron microscope.The average particle diameter was determined by measuring the particlediameters of any 30 particles and calculating their number-averageparticle diameter. These are the same also in such as the followingexamples.

EXAMPLE 2

The same pot as used in Example 1 was charged with 65 parts ofstainless-steel (SUS316)-made balls having a diameter of 5 mmφ (as ballsfor polish-pulverization), 5 parts of CdSe (as the compoundsemiconductor), and 3 parts of methanol (as the solvent), and then thepot was tightly shut.

This pot was set to a ball mill apparatus to make revolution at a setrevolution rate of the pot of 229 rpm and a set revolution rate of thedisk of 107 rpm for 40 hours, thus carrying out the polish-pulverizationtreatment.

After the above treatment (revolution for 40 hours), there were takenout the stainless-steel (SUS316)-made balls for the polish-pulverizationhaving a diameter of 5 mmφ, and then instead thereof stainless-steel(SUS316)-made balls for polish-pulverization having a diameter of 3 mmφwere charged into the pot. Then, the revolution was made for 52 hoursunder the same revolution rate conditions as of the preceding treatment,thus carrying out the polish-pulverization treatment.

Furthermore, after the above treatment (revolution for 52 hours), therewere taken out the stainless-steel (SUS316)-made balls for thepolish-pulverization having a diameter of 3 mmφ, and then insteadthereof stainless-steel (SUS316)-made balls for polish-pulverizationhaving a diameter of 1 mmφ were charged into the pot. Then, therevolution was made for 87 hours under the same revolution rateconditions as of the preceding treatment, thus carrying out thepolish-pulverization treatment.

After all the polish-pulverization treatments, there was obtained adispersion (2a) of compound semiconductor particles by filtrating thecontents as obtained in the pot. As a result of observation of thedispersion (2a) with a TEM, it was confirmed that CdSe particles(compound semiconductor particles) having an average particle diameterof 0.03 μm were formed in the dispersion (2a) wherein a portion of theCdSe particles were fine CdSe particles having particle diameters ofabout 19 nm and fine CdSe particles having particle diameters of notlarger than 10 nm (as shown in FIG. 2).

EXAMPLE 3

There was obtained a dispersion (3a) of compound semiconductor particlesin the same way as of Example 2 except to replace the 5 parts of CdSewith 5 parts of ZnS. As a result of observation of the dispersion (3a)with a TEM, it was confirmed that fine ZnS particles (compoundsemiconductor particles) having an average particle diameter of 0.03 μmwere formed in the dispersion (3a) wherein a portion of the ZnSparticles were fine ZnS particles having particle diameters of notlarger than 10 nm.

EXAMPLE 4

There was prepared a reaction apparatus having a stainless-steel(SUS316)-made reactor of 1 L. Incidentally, this stainless-steel-madereactor is a reactor having the pressure resistance to 10 MPa, whereinthe reactor is equipped with an addition tank having a stirrer, anaddition inlet as directly connected to the addition tank, and athermometer, and can be heated from the outside.

The reactor was charged with 16 parts of the dispersion (2a) as obtainedin Example 2, 18 parts of zinc acetate, and 800 parts of methanol. Theresultant mixture was heated to 150° C. under stirred conditions.Thereafter, the mixture was maintained at 150° C. for 1 hour andthereafter cooled, thus obtaining a reaction liquid (4b).

While fine particles as contained in the resultant reaction liquid (4b)were observed with an FE-TEM (field emission type transmission electronmicroscope) as equipped with an XMA apparatus (X-ray microanalyzer)having the resolving power of 1 nmφ, the elemental analysis of the abovefine particles was carried out. As a result, it was confirmed that thefine particles were fine CdSe particles covered with zinc oxide (ZnO).Furthermore, the fine particles as obtained were subjected to such asthe ion chromatographic analysis, the TG-DTA analysis, and thetemperature-raising elimination analysis using a heating furnace asdirectly connected to a GC-MS. As a result, it was confirmed that theZnO, as provided to the covering, contained the acetoxy group in abonded state in an amount of 1 weight % relative to the ZnO (1.38 mol %relative to Zn).

EXAMPLE 5

There was prepared the same reaction apparatus as used in Example 4.

The reactor was charged with 16 parts of the dispersion (3a) as obtainedin Example 3 and 700 parts of n-butanol. The resultant mixture washeated to 180° C. under stirred conditions.

In addition, the addition tank was charged with 100 parts of a indiumacetate dispersion as obtained by dispersing 44 parts of indium acetateinto n-butanol. The time of addition of this indium acetate dispersionwas divided into 10 times, and the indium acetate dispersion was addedin an amount of 10 parts each at intervals of 20 minutes. After thisaddition, the resultant mixture was maintained at 180° C. for 1 hour andthereafter cooled, thus obtaining a reaction liquid (5b).

While fine particles as contained in the resultant reaction liquid (5b)were observed with the same FE-TEM (field emission type transmissionelectron microscope) as used in Example 4, the elemental analysis of theabove fine particles was carried out. As a result, it was confirmed thatthe fine particles were fine ZnS particles covered with indium oxide(In₂O₃). Furthermore, the fine particles as obtained were subjected tosuch as the ion chromatographic analysis, the TG-DTA analysis, and thetemperature-raising elimination analysis using a heating furnace asdirectly connected to a GC-MS. As a result, it was confirmed that theIn₂O₃, as provided to the covering, contained the acetoxy group in abonded state in an amount of 5 weight % relative to the In₂O₃ (11.8 mol% relative to In).

EXAMPLE 6

The same pot as used in Example 1 was charged with 65 parts ofstainless-steel (SUS316)-made balls having a diameter of 5 mmφ (as ballsfor polish-pulverization), 5 parts of CdSe (as the compoundsemiconductor (coarse particles of a compound semiconductor)), and 10parts of hexane (as the solvent), and then the pot was tightly shut.

This pot was set to a ball mill apparatus to make revolution at a setrevolution rate of the pot of 229 rpm and a set revolution rate of thedisk of 107 rpm for 1 hour, thus carrying out the polish-pulverizationtreatment.

After the polish-pulverization treatment, 0.16 part of acetic acid(acetic acid/Cd=0.1 (molar ratio)) was added to the contents as obtainedin the pot, and the resultant mixture was stirred for 1 hour, andthereafter the mixture was filtrated, thus obtaining a dispersion (6a)of compound semiconductor particles.

While fine particles as contained in the resultant dispersion (6a) wereobserved with the FE-TEM as equipped with the XMA apparatus having theresolving power of 1 nmφ in the same way as of Example 4, the elementalanalysis of the above fine particles was carried out. As a result, itwas confirmed that: in the dispersion (6a), there were dispersed CdSeparticles (compound semiconductor particles) having particle diametersof 0.2 to 1.0 μm in an amount of 10 wt %, and further there existed fineparticles as impurities different from the CdSe though being a trace.

Accordingly, the centrifugal separation treatment of the dispersion (6a)was carried out to thereby sediment the fine CdSe particles. After thesupernatant had been separated, the sediment was washed with hexane andthen re-dispersed into 2-butoxyethanol. The polish-pulverizationtreatment was carried out again for 10 hours, and then the contents asobtained in the pot were filtrated, thus obtaining a dispersion (6a′) ofcompound semiconductor particles.

While fine particles as contained in the dispersion (6a′) were observedwith the FE-TEM as equipped with the XMA apparatus having the resolvingpower of 1 nmφ in the same way as of Example 4, the elemental analysisof the above fine particles was carried out. As a result, it wasconfirmed that, in the dispersion (6a′), there were dispersed fine CdSeparticles (compound semiconductor particles) having particle diametersof 50 to 300 nm in an amount of 10 wt %.

On the other hand, the above separated supernatant was concentrated withan evaporator. While fine particles as contained in the resultantconcentrate were observed with the FE-TEM as equipped with the XMAapparatus having the resolving power of 1 nmφ in the same way as ofExample 4, the elemental analysis of the above fine particles wascarried out. As a result, it was confirmed that there existed fine Cuparticles, fine CuSe particles, and fine Se particles having particlediameters of 5 to 20 nm.

There was carried out the ICP analysis of the Cu content of the compoundsemiconductor CdSe (coarse particles of the compound semiconductor) usedas raw materials. As a result, the above content was 0.5 ppm, but the Cucontent of the dispersion (6a′) was less than 0.1 ppm relative to theCdSe.

COMPARATIVE EXAMPLE 1

For comparison, there was obtained a 2-butoxyethanol dispersion (C1a) bycarrying out the same procedure as of Example 6, except to add no aceticacid. As a result, neither fine Cu particles nor fine CuSe particleswere detected in the supernatant resultant from the centrifugalseparation treatment, and the Cu content of the dispersion (C1a) was 0.5ppm relative to the CdSe.

EXAMPLE 7

A mixture, as obtained by adding and mixing 10 parts of zinc acetateinto 100 parts of the dispersion (6a′) as obtained in Example 6, wascharged into the same reactor of the same reaction apparatus as used inExample 4, and this mixture was stirred and heated from ordinarytemperature (25° C.) to 120° C. While being maintained at 120±2° C., themixture was heat-treated for 30 minutes and then cooled, thus obtaininga reaction liquid (7b).

While fine particles as contained in the reaction liquid (7b) wereobserved with the FE-TEM as equipped with the XMA apparatus having theresolving power of 1 nmφ in the same way as of Example 4, the elementalanalysis of the above fine particles was carried out. As a result, itwas confirmed that, in the reaction liquid (7b), there were dispersedfine CdSe particles which had particle diameters of about 50 to about350 nm and were covered with ZnO.

A TEM image of the analyzed fine CdSe particles is shown in FIG. 3, andan example of the results of the elemental analysis of the fine CdSeparticles by the energy-dispersive X-ray analysis method is shown inFIG. 4. From FIGS. 3 and 4, it can be understood that the fine CdSeparticles having particle diameters of about 240 nm are covered with aZnO layer having a thickness of about 20 to about 30 nm.

EXAMPLES 8 TO 11

In accordance with the charging composition as listed in Table 2, thesame pot as used in Example 1 was charged with the raw materials aslisted in Table 1, the below-mentioned media for polish-pulverization,the solvents as listed in Table 2, and the additives as listed in Table2. Then, the pot was tightly shut and then set to a ball mill apparatusto carry out the polish-pulverization treatment under the followingconditions.

First, a mixture of stainless-steel (SUS316)-made balls having adiameter of 1 mmφ and Y-containing zirconia beads (ZrO₂(Y)) having adiameter of 0.1 mmφ (weight ratio=1:1) was used as the media forpolish-pulverization to carry out the polish-pulverization treatment bymaking revolution at a set revolution rate of the pot of 1,000 rpm and aset revolution rate of the disk of 139 rpm for 1 hour.

After the above treatment (revolution for I hour), there were taken outthe mixture of the stainless-steel (SUS316)-made balls having a diameterof 1 mmφ and the Y-containing zirconia beads (ZrO₂(Y)) having a diameterof 0.1 mmφ, and then instead thereof Y-containing zirconia beads(ZrO₂(Y)) having a diameter of 0.05 mmφ were charged into the pot. Then,the revolution was made at a set revolution rate of the pot of 100 rpmand a set revolution rate of the disk of 100 rpm for 10 hours, thuscarrying out the polish-pulverization treatment.

Thereafter, while the same solvent as the used solvent was auxiliarilyused to extract the particles from the pot together with the solvent,the contents of the pot were filtrated, thus obtaining a dispersion ofcompound semiconductor particles.

Furthermore, when the occasion demanded as listed in Table 2, aprimary-particle formation promoter was added to carry out themonodispersing treatment, and then the resultant mixture was filtrated,thus obtaining dispersions (8a) to (11a) of the compound semiconductorparticles as listed in Table 3.

Next, as to the resultant dispersions (8a) to (11a) of the compoundsemiconductor particles, the particles were covered under conditions aslisted in Table 4, thus obtaining dispersions (8b) to (11b) of thecovered compound semiconductor particles. The results of the analysis ofthe resultant particles are listed in Table 5.

Hereupon, in Example 8, the dispersion to be subjected to the coveringwas used after being diluted with the same solvent as that in thedispersion into the concentration as listed in Table 4.

Incidentally, the reaction methods A, B, and C for the covering aslisted in Table 4 are as follows.

Reaction method A: The same pressure-resistant reactor as used inExample 4 was charged with the dispersion of the compound semiconductorparticles and a liquid (solution or slurry) including a raw material forthe covering, and the resultant mixture was heated under stirredconditions and then maintained at the temperature as listed in Table 4.

Reaction method B: The same pressure-resistant reactor as used inExample 4 was charged with the dispersion of the compound semiconductorparticles. On the other hand, the addition tank was charged with aliquid (solution or slurry) including a raw material for the covering.The dispersion of the compound semiconductor particles was heated understirred conditions and then maintained at the temperature as listed inTable 4. Thereafter, the liquid (solution or slurry) including the rawmaterial for the covering was added (divisionally added or continuouslyfed) from the addition tank, and the resultant mixture was maintained atthe above temperature for the time as listed in Table 4.

Reaction method C: A mixture, as obtained by mixing the dispersion ofthe compound semiconductor particles and a liquid (solution or slurry)including a raw material for the covering with a mixer, was passedthrough a SUS-made tube reactor (inner diameter: 20 mmφ) as immersed ina heat medium, thus carrying out a reaction at the temperature (whichwas the set temperature of the tube reactor) for the time as listed inTable 4.

EXAMPLES 12 TO 14

In accordance with the charging composition as listed in Table 2, thesame pot as used in Example 1 was charged with the raw materials aslisted in Table 1, the below-mentioned media for polish-pulverization,the solvents as listed in Table 2, and the additives as listed in Table2. Then, the pot was tightly shut and then set to a ball mill apparatusto carry out the polish-pulverization treatment under the followingconditions.

A mixture of stainless-steel (SUS316)-made balls having a diameter of 5mmφ, stainless-steel (SUS316)-made balls having a diameter of 3 mmφ,stainless-steel (SUS316)-made balls having a diameter of 1 mmφ, andY-containing zirconia beads (ZrO₂(Y)) having a diameter of 0.05 mmφ(weight ratio=1:1:1:2) was used as the media for polish-pulverization tocarry out the polish-pulverization treatment by making revolution at aset revolution rate of the pot of 1,000 rpm and a set revolution rate ofthe disk of 139 rpm for 10 hours.

Thereafter, while the same solvent as the used solvent was auxiliarilyused to extract the particles from the pot together with the solvent,the contents of the pot were filtrated, thus obtaining a dispersion ofcompound semiconductor particles.

Furthermore, when the occasion demanded as listed in Table 2, aprimary-particle formation promoter was added to carry out themonodispersing treatment, and then the resultant mixture was filtrated,thus obtaining dispersions (12a) to (14a) of the compound semiconductorparticles as listed in Table 3.

Next, as to the resultant dispersions (12a) to (14a) of the compoundsemiconductor particles, the particles were covered under conditions aslisted in Table 4, thus obtaining dispersions (12b) to (14b) of thecovered compound semiconductor particles. The results of the analysis ofthe resultant particles are listed in Table 5.

Hereupon, in Example 12, the dispersion to be subjected to the coveringwas used after being diluted with the same solvent as that in thedispersion into the concentration as listed in Table 4.

Incidentally, the reaction methods A, B, and C for the covering aslisted in Table 4 are as aforementioned.

EXAMPLES 15 TO 18

In accordance with the charging composition as listed in Table 2, thesame pot as used in Example 1 was charged with the raw materials aslisted in Table 1, the below-mentioned media for polish-pulverization,the solvents as listed in Table 2, and the additives as listed in Table2. Then, the pot was tightly shut and then set to a ball mill apparatusto carry out the polish-pulverization treatment under the followingconditions.

First, stainless-steel (SUS316)-made balls having a diameter of 1 mmφwere used as the media for polish-pulverization to carry out thepolish-pulverization treatment by making revolution at a set revolutionrate of the pot of 1,000 rpm and a set revolution rate of the disk of1,000 rpm for 3 hours.

After the above treatment (revolution for 3 hours), there were taken outthe stainless-steel (SUS316)-made balls having a diameter of 1 mmφ, andthen instead thereof Y-containing zirconia beads (ZrO₂(Y)) having adiameter of 0.1 mmφ were charged into the pot. Then, the revolution wasmade at a set revolution rate of the pot of 800 rpm and a set revolutionrate of the disk of 139 rpm for 1 hour, thus carrying out thepolish-pulverization treatment.

After the above treatment (revolution for 1 hour), there were taken outthe Y-containing zirconia beads (ZrO₂(Y)) having a diameter of 0.1 mmφ,and then instead thereof Y-containing zirconia beads (ZrO₂(Y)) having adiameter of 0.05 mmφ were charged into the pot. Then, the revolution wasmade at a set revolution rate of the pot of 400 rpm and a set revolutionrate of the disk of 139 rpm for 1 hour, thus carrying out thepolish-pulverization treatment.

Thereafter, while the same solvent as the used solvent was auxiliarilyused to extract the particles from the pot together with the solvent,the contents of the pot were filtrated, thus obtaining a dispersion ofcompound semiconductor particles.

Furthermore, when the occasion demanded as listed in Table 2, aprimary-particle formation promoter was added to carry out themonodispersing treatment, and then the resultant mixture was filtrated,thus obtaining dispersions (15a) to (18a) of the compound semiconductorparticles as listed in Table 3.

Next, as to the resultant dispersions (15a) to (18a) of the compoundsemiconductor particles, the particles were covered under conditions aslisted in Table 4, thus obtaining dispersions (15b) to (18b) of thecovered compound semiconductor particles. The results of the analysis ofthe resultant particles are listed in Table 5.

Hereupon, in Example 18, the dispersion to be subjected to the coveringwas used after being concentrated into the concentration as listed inTable 4 by removing a portion of the solvent by heating under reducedpressure with an evaporator.

Incidentally, the reaction methods A, B, and C for the covering aslisted in Table 4 are as aforementioned.

EXAMPLES 19 TO 22

The dispersions (8a) to (10a) and (12a) to be subjected to the coveringin Examples 8 to 10 and 12 were heat-treated under conditions as listedin Table 6 before the covering, and thereafter the covering was carriedout under the same conditions as of Examples 8, 9, 10, and 12, thusobtaining dispersions (19b) to (22b) of the covered compoundsemiconductor particles.

EXAMPLE 23

The dispersion (8b) of the covered compound semiconductor particles, asobtained in Example 8, was heat-treated at 200° C. for 1 hour, thusobtaining a dispersion (23b) of the covered compound semiconductorparticles.

EXAMPLE 24

The dispersion (12b) of the covered compound semiconductor particles, asobtained in Example 12, was heat-treated at 250° C. for 1 hour, thusobtaining a dispersion (24b) of the covered compound semiconductorparticles.

EXAMPLE 25

A CaS:Ce (Ce/Ca=0.2 atm %) polycrystal (average particle diameter: 1 μm)was preliminarily polish-pulverized by using the same apparatus as usedin Example 1, thus preparing a slurry including a methanol solvent andCaS:Ce particles (TEM particle diameter: 8 nm, dispersed-particlediameter: 200 nm) that were dispersed and contained in the methanolsolvent in an amount of 5 wt %. Next, the same apparatus as used inExample 1 was charged with a mixture including 20 parts of the aboveslurry, 10 parts of zinc acetate (as the raw metal material for thecovering metal oxide), and 0.01 part of acetic acid and with 10 parts ofzirconia beads (ZrO₂: Y) having a diameter of 0.05 μmφ (as the media).Then, the polish-pulverization treatment was carried out for 100 hoursunder conditions of revolution rate of the pot=500 rpm and revolutionrate of the disk=50 rpm. The resultant contents were filtrated, thusobtaining a dispersion (25b) including methanol and particles (particleconcentration: 5 wt %, dispersed-particle diameter: 20 nm, TEM particlediameter: 12 nm) that were dispersed in the methanol.

As a result of the analysis of the particles in the dispersion (25b) asobtained, it was found that the CaS:Ce having a crystal grain diameterof 5 nm was covered with a ZnO layer having a thickness of 2 to 3 nm.

EXAMPLE 26

The reaction liquid (4b), as obtained in Example 4, and the dispersions(8b) to (10b), (12b), and (19b) to (24b) as obtained in Examples 8 to10, 12, and 19 to 24, were evaluated by the photoluminescence property.The evaluation results are listed in Table 7.

It was found that the particles as contained in any dispersion emitlight in the luminescence colors as listed in Table 7.

EXAMPLE 27

The reaction liquid (4b), as obtained in Example 4, and the dispersions(8b) to (10b), (12b), and (19b) to (24b) as obtained in Examples 8 to10, 12, and 19 to 24, were evaluated by the fluorescence property due tothe light source of the ultraviolet-light-emitting diode. The evaluationresults are listed in Table 8.

As is shown in Table 8, it was found that the particles as contained inany dispersion emit light in the same luminescence colors as listed inTable 7.

In addition, it was found that the fluorescence of the particles, ascontained in the dispersions (19b) to (24b) as obtained in Examples 19to 24 in which the heat treatment was carried out, is more intense thanthat of the particles as contained in the dispersions as obtained intheir respective corresponding Examples (Examples 8, 9, 10, 12, 8, and12 in order) in which the heat treatment was not carried out.

COMPARATIVE EXAMPLE 2

There was prepared 100 parts of an ethanol dispersion including ZnS—Mnparticles (Mn/Zn=0.3 atm %, particle diameter as found with TEM=3 to 5nm) in an amount of 1 wt %, wherein the ethanol dispersion was obtainedby a liquid phase method (including the steps of: adding a methanolsolution of zinc acetate and manganese acetate to an aqueous sodiumsulfide solution; and then collecting the resultant precipitate bycentrifugal separation; and then washing the precipitate with methanol;and then dispersing the precipitate into ethanol).

While this dispersion was stirred, 2 parts of ammonia water (NH₃content: 1%) was added thereto as the catalyst for hydrolysis, andthereafter 10 parts of an ethanol solution containing tetramethoxysilanein an amount of 10 wt % was further added.

The dispersion as obtained this way was a liquid having a high tendencyto involve sedimentation. The particles in this liquid were particleswhich had formed an aggregate by aggregation of silica and ZnS—Mnparticles in large numbers, so it was difficult to say that the ZnS—Mnparticles were covered with the silica.

COMPARATIVE EXAMPLE 3

The same procedure as of Comparative Example 2 was carried out except toreplace the catalyst for hydrolysis with 2 parts of an aqueous solutioncontaining acetic acid in an amount of 1 wt %.

The resultant dispersion was a liquid having a high tendency to involvesedimentation. The particles in this liquid were particles which hadformed an aggregate by aggregation of silica and ZnS—Mn particles inlarge numbers, so it was difficult to say that the ZnS—Mn particles werecovered with the silica. TABLE 1 Composition of raw materialClassification Dopant/M Composition of Crystal structure Averageparticle Example of compound Raw material (atm %) mixed crystal of rawmaterial diameter 8 II-VI ZnS:Mn(II) 0.03 — Polycrystal 1.2 μm  9 II-VIY₂O₃S:Eu(III) 0.1 — Polycrystal 3.2 μm  10 IIa-VI SrS:Tb(III) 0.5 —Polycrystal 50 μm 11 IIa-VI CaS:Sm(III) 1 — Polycrystal 50 μm 12 II-VIZnS:Cu(II) 1.5 — Polycrystal 12 μm 13 II-VI ZnSSe:Mn(II) 0.8 S/Se = 8/2Polycrystal 5.3 μm  mixed crystal 14 II-VI ZnMgS 0 Zn/Mg = 9/1Polycrystal 11 μm mixed crystal 15 III-V AlInP 0 Al/In = 7/3 Polycrystal14 μm mixed crystal 16 IV—IV SiC 0 — Polycrystal 1.5 μm  17 IV-VI PbTe 0— Polycrystal 3.3 μm  18 II-VI CaSrS:Ce 1.1 Ca/Sr = 1/1 Polycrystal   1mmM: This denotes being based on the metal in the raw material

TABLE 2 Monodispersing treatment Charging composition conditionsAdditive Additive Raw (primary-particle Amount of Monodispersing(primary-particle Amount of material Solvent Media Composition formationadditive treatment formation additive Example (parts) (parts) (parts) ofsolvent promoter) (mol %/M) apparatus promoter) (mol %/M) 8 5 3 65Methanol None — Beads mill Acetic acid 1 9 5 3 65 Ethanol None —Homogenizer None — 10 5 3 65 Benzyl 2-Ethylhexanoic 1 Homogenizer None —alcohol acid 11 5 3 65 EGDME Acetic acid 1 None None — 12 5 3 65Methanol None — Homomixer Acetic acid 0.1 13 5 3 65 Methanol None —Stirring Acetic acid 0.01 14 5 3 65 IPA None — Beads mill Propionic 10acid 15 5 3 65 Ethanol Propionic 10 None None — acid 16 5 3 65 PGMAcNone — None None — 17 5 3 65 Butyl Lauric acid 0.1 Paint shaker None —acetate 18 5 3 65 Methanol Acetic acid 1 None None —EGDME: Ethylene glycol dimethyl etherPGMAc: Propylene glycol methyl ether acetateM in unit of amount of additive: This denotes being based on the metalin the raw materialBeads mill: Y-containing zirconia beads having a diameter of 50 μmφ wereused as the media.

TABLE 3 Dispersion of Dispersed- compound Particle particle TEM particleCrystal grain semiconductor concentration diameter diameter diameterExample particles (wt %) Solvent (nm) (nm) (nm) 8  (8a) 12 Methanol 8 43 9  (9a) 3 Ethanol 23 10 8 10 (10a) 6 Benzyl alcohol 60 20 18 11 (11a)10 EGDME 18 12 12 12 (12a) 10 Methanol 30 20 18 13 (13a) 8 Methanol 2413 13 14 (14a) 0.5 IPA 10 5 4 15 (15a) 10 Ethanol 12 9 7 16 (16a) 1PGMAc 73 11 10 17 (17a) 15 Butyl acetate 20 8 7 18 (18a) 18 Methanol 167 5EGDME: Ethylene glycol dimethyl etherPGMAc: Propylene glycol methyl ether acetate

TABLE 4 Dispersion Covering reaction conditions to be covered Rawmaterial liquid (solution or slurry) for covering Addition Amount AmountCarboxyl-group- method in of of Raw metal containing Exam- Reaction caseof Heating temperature × dispersion particles material Solvent compoundple method method B heating time (parts) (parts) Kind Parts Kind PartsKind Parts 8 A — 120° C. × 1 hour 100 5 Zinc 26 Methanol 0 — —propionate 9 B 10 divisional Addition of raw covering 100 3 Tin (IV) 28Ethanol 30 — — additions at material at 150° C. and acetate intervals ofthereafter heating for 1 10 minutes hour 10 C — 200° C. × 10 minutes 1006 Zirconium 16 Benzyl 100 — — 2-ethyl- alcohol hexanoate 11 C — 180° C.× 10 minutes 100 10 Hafnium 170 EGDME 1000 Acetic 100 n-butoxide acid 12C — 120° C. × 10 minutes 100 1 Zinc acetate 28 Methanol 200 — — Indiumacetate 0.45 13 B Feeding at a Addition of raw covering 100 8 Bismuth(III) 20 Methanol 40 — — constant rate material at 200° C. and acetateoxide for 2 hours thereafter heating for 1 hour 14 A — 200° C. × 1 hour100 0.5 Yttrium acetate 4.5 IPA 0 — — tetrahydrate 15 C — 200° C. × 10minutes 100 10 Iron (III) 643 n-Butanol 1000 — — acetate, basic 16 BFeeding at a Addition of raw covering 100 1 Titanium (IV) 30 PGMAc 70Propionic 10 constant rate material at 180° C. and t-butoxide acid for 2hours thereafter heating for 1 hour 17 A — 200° C. × 10 minutes 100 15Methyltri- 0.6 Butyl 0 Formic 3 methoxysilane acetate acid 18 A — 200°C. × 1 hour 100 30 Lanthanum (III) 2.9 Methanol 0 — — acetateEGDME: Ethylene glycol dimethyl ether,PGMAc: Propylene glycol methyl ether acetate

TABLE 5 Results of analysis of dispersion of covered compoundsemiconductor particles Bonding amount of Dispersed- TEM acyloxyl groupparticle particle Form of Film thickness (mol %/metal Exam- diameterdiameter covering of covering Major component component of pleDispersion (nm) (nm) Form layer layer (nm) of covering layer Acyloxylgroup covering layer) 8  (8b) 12 5.5 Core- Uniform 0.7 (Zn—O)-majorPropionyloxy 12 shell film component 9  (9b) 28 16 Core- Uniform 2.7 Tin(IV) oxide Acetoxy 5 shell film (Ethanoyloxy) 10 (10b) 63 24 Core-Uniform 1.4 Zirconium oxide 2-Ethylhexanoyloxy 1 shell film 11 (11b) 2120 Core- Uniform 7 Hafnium oxide Acetoxy 0.3 shell film 12 (12b) 35 32Core- Uniform 11 Zinc oxide Acetoxy 0.5 shell film crystal In/Zn = 1 atm% 13 (13b) 29 16 Core- Uniform 3 Bismuth oxide Acetoxy 8 shell film 14(14b) 11 6.3 Core- Uniform 1.2 Yttrium oxide Acetoxy 12 shell film 15(15b) 18 16 Core- Uniform 7 Magnetite Acetoxy 9 shell film crystal 16(16b) 90 16 Core- Uniform 5 Titanium oxide Propionyloxy 0.1 shell film(anatase) 17 (17b) 40 8 Core- Formation <0.2 Polymethyl- None — shell ofalmost siloxane-major single- component molecular layer film 18 (18b) 147 Core- Attachment <0.2 (La—O)-major Acetoxy 27 shell of fine componentparticulate substanceHydrolyzed and condensed product from MTMS: Hydrolyzed and condensedproduct from methyltrimethoxysilanePolymethylsiloxane: (—Si(CH₃)—O—)_(n)

TABLE 6 Heat-treatment conditions Dispersion to be Pressure Exampleheat-treated Heating conditions conditions 19  (8a) Temperature wasraised from Applied ordinary temperature and then pressure maintained at100° C. for 1 hour. 20  (9a) Temperature was raised from Appliedordinary temperature and then pressure maintained at 150° C. for 1 hour.21 (10a) Temperature was raised from Applied ordinary temperature andthen pressure maintained at 250° C. for 10 minutes. 22 (12a) Temperaturewas raised from Applied ordinary temperature and then pressuremaintained at 200° C. for 1 minute.

TABLE 7 Reaction liquid or dispersion Evaluation of photoluminescence tobe evaluated property Luminescence color Reaction liquid (4b) RedDispersion (8b) Yellow Dispersion (9b) Red Dispersion (10b) GreenDispersion (12b) Blue Dispersion (19b) Yellow Dispersion (20b) RedDispersion (21b) Green Dispersion (22b) Blue Dispersion (23b) YellowDispersion (24b) Blue

TABLE 8 Evaluation of fluorescence property due to light Reaction liquidsource of ultraviolet-light-emitting diode or dispersion Luminescence tobe evaluated color Luminosity Reaction liquid (4b) Red — Dispersion (8b)Yellow — Dispersion (9b) Red — Dispersion (10b) Green — Dispersion (12b)Blue — Dispersion (19b) Yellow More intense than dispersion (8a)Dispersion (20b) Red More intense than dispersion (9a) Dispersion (21b)Green More intense than dispersion (10a) Dispersion (22b) Blue Moreintense than dispersion (12a) Dispersion (23b) Yellow More intense thandispersion (8a) Dispersion (24b) Blue More intense than dispersion (12a)

INDUSTRIAL APPLICATION

The compound semiconductor particles according to the present invention,or the compound semiconductor particles as obtained by the productionprocess according to the present invention, can be used, for example, asluminophors having a high-efficient luminescence property, specifically,as fluophor particles of various colors (e.g. red (R), green (G), blue(B), and yellow (Y)) and as luminophor particles being in theultraviolet or infrared wavelength range. In addition, as to medicaluses, the above particles can be used also for tumor markers, curingmedicines, and examining agents for the purpose of detection of tumors(e.g. cancers) or examination of such as their progress conditions.Furthermore, the above particles can be used also for various sensors(e.g. biosensors; sensors for search of land mines, TNT(trinitrotoluene), and earth vein; and ultraviolet sensors) andwavelength-converting films.

1. A production process for compound semiconductor particles, whichcomprises the step of heating and/or polish-pulverizing a mixtureincluding a metal carboxylate, an alcohol, and particles or a mixtureincluding a metal-alkoxy-group-containing compound, acarboxyl-group-containing compound, and particles, thereby covering theparticles with a metal oxide, wherein the particles include a compoundsemiconductor.
 2. A production process for compound semiconductorparticles according to claim 1, wherein the particles including thecompound semiconductor are particles as obtained by a process includingthe step of polish-pulverizing coarse particles of the compoundsemiconductor to thereby fine the particles.
 3. A production process forcompound semiconductor particles, which comprises the steps of:polish-pulverizing coarse particles of a compound semiconductor tothereby obtain particles having particle diameters of smaller than 1 μm;and then covering the resultant particles with a metal oxide. 4.Compound semiconductor particles, which comprise body particles and ametal oxide, wherein the body particles have particle diameters ofsmaller than 1 μm and are covered with the metal oxide and include acompound semiconductor including an essential element combination of atleast one element X selected from the group consisting of C, Si, Ge, Sn,Pb, N, P, As, S, Sb, Se, and Te and at least one metal element M that isnot identical with the element X, and wherein the metal oxide is a metaloxide to which an acyloxyl group is bonded.
 5. Compound semiconductorparticles according to claim 4, wherein the body particles are particlesas obtained by a process including the step of polish-pulverizing coarseparticles of the compound semiconductor including the essential elementcombination of at least one element X selected from the group consistingof C, Si, Ge, Sn, Pb, N, P, As, Sb, S, Se, and Te and at least one metalelement M that is not identical with the element X.